clean install

web/modules/consumers/src/AccessControlHandler.php

@@ -0,0 +1,65 @@
+<?php
+
+namespace Drupal\consumers;
+
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Entity\EntityAccessControlHandler;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Session\AccountInterface;
+
+/**
+ * Access controller for the Access Token entity.
+ *
+ * @see \Drupal\consumers\Entity\Consumer.
+ */
+class AccessControlHandler extends EntityAccessControlHandler {
+
+  /**
+   * The entity id.
+   *
+   * @var string
+   */
+  public static $name = 'consumer';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
+    /** @var \Drupal\consumers\Entity\ConsumerInterface $entity */
+    $admin_permission = $this->entityType->getAdminPermission();
+    if ($account->hasPermission($admin_permission)) {
+      return AccessResult::allowed()->cachePerPermissions();
+    }
+
+    // Permissions only apply to own entities.
+    $is_owner = ($account->id() && $account->id() === $entity->getOwnerId());
+    $is_owner_access = AccessResult::allowedIf($is_owner)
+      ->addCacheableDependency($entity);
+    $operations = ['view', 'update', 'delete'];
+    if (!in_array($operation, $operations)) {
+      $reason = sprintf(
+        'Supported operations on the entity are %s',
+        implode(', ', $operations)
+      );
+      return AccessResult::neutral($reason);
+    }
+
+    return $is_owner_access->andIf(AccessResult::allowedIfHasPermission(
+      $account,
+      sprintf('%s own %s entities', $operation, static::$name)
+    )->cachePerPermissions());
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkCreateAccess(AccountInterface $account, array $context, $entity_bundle = NULL) {
+    $admin_access = parent::checkCreateAccess($account, $context, $entity_bundle);
+
+    return $admin_access->orIf(AccessResult::allowedIfHasPermission(
+      $account,
+      sprintf('add %s entities', static::$name),
+    ));
+  }
+
+}

web/modules/consumers/src/ConsumerListBuilder.php

@@ -0,0 +1,75 @@
+<?php
+
+namespace Drupal\consumers;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityListBuilder;
+
+/**
+ * Defines a class to build a listing of Access Token entities.
+ */
+class ConsumerListBuilder extends EntityListBuilder {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildHeader() {
+    $header['client_id'] = $this->t('Client ID');
+    $header['uuid'] = $this->t('UUID');
+    $header['label'] = $this->t('Label');
+    $header['is_default'] = $this->t('Is Default?');
+    $context = ['type' => 'header'];
+    $this->moduleHandler()->alter('consumers_list', $header, $context);
+    $header = $header + parent::buildHeader();
+    return $header;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildRow(EntityInterface $entity) {
+    /** @var \Drupal\consumers\Entity\ConsumerInterface $entity */
+    $row['client_id'] = $entity->getClientId();
+    $row['uuid'] = $entity->uuid();
+    $row['label'] = $entity->toLink();
+    $ops = [
+      '#type' => 'operations',
+      '#links' => [
+        [
+          'title' => $this->t('Make Default'),
+          'url' => $entity->toUrl('make-default-form', [
+            'query' => $this->getDestinationArray(),
+          ]),
+        ],
+      ],
+    ];
+    $row['is_default'] = $entity->get('is_default')->value
+      ? ['data' => $this->t('Default')]
+      : ['data' => $ops];
+
+    $context = ['type' => 'row', 'entity' => $entity];
+    $this->moduleHandler()->alter('consumers_list', $row, $context);
+    $row = $row + parent::buildRow($entity);
+    return $row;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getOperations(EntityInterface $entity) {
+    $operations = parent::getOperations($entity);
+    if (
+      $entity->access('update') &&
+      $entity->hasLinkTemplate('make-default-form') &&
+      !$entity->get('is_default')->value
+    ) {
+      $operations['make-default'] = [
+        'title' => $this->t('Make Default'),
+        'weight' => 10,
+        'url' => $this->ensureDestination($entity->toUrl('make-default-form')),
+      ];
+    }
+    return $operations;
+  }
+
+}

web/modules/consumers/src/ConsumerRouteEnhancer.php

@@ -0,0 +1,69 @@
+<?php
+
+namespace Drupal\consumers;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Routing\EnhancerInterface;
+use Drupal\jsonapi\Routing\Routes;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Adds appropriate cache contexts if a consumer request is made.
+ */
+class ConsumerRouteEnhancer implements EnhancerInterface {
+
+  /**
+   * The cache context by which vary the loaded data.
+   *
+   * @var string
+   */
+  const CACHE_CONTEXT = 'url.query_args:consumerId';
+
+  /**
+   * The consumer negotiator.
+   *
+   * @var \Drupal\consumers\Negotiator
+   */
+  protected $consumerNegotiator;
+
+  /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * ConsumerRouteEnhancer constructor.
+   *
+   * @param \Drupal\consumers\Negotiator $negotiator
+   *   The consumer negotiator.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   */
+  public function __construct(Negotiator $negotiator, ModuleHandlerInterface $module_handler) {
+    $this->consumerNegotiator = $negotiator;
+    $this->moduleHandler = $module_handler;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function enhance(array $defaults, Request $request) {
+    if (!$this->moduleHandler->moduleExists('jsonapi') ||
+      !Routes::isJsonApiRequest($defaults) ||
+      !Routes::getResourceTypeNameFromParameters($defaults)
+    ) {
+      return $defaults;
+    }
+
+    if (isset($defaults['entity'])) {
+      assert($defaults['entity'] instanceof EntityInterface);
+      $defaults['entity']->addCacheContexts([static::CACHE_CONTEXT]);
+    }
+
+    return $defaults;
+  }
+
+}

web/modules/consumers/src/ConsumerStorage.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Drupal\consumers;
+
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\Sql\SqlContentEntityStorage;
+
+/**
+ * Defines the storage handler class for consumers.
+ *
+ * This extends the base storage class, adding required special handling for
+ * consumers.
+ */
+class ConsumerStorage extends SqlContentEntityStorage {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function restore(EntityInterface $entity) {
+    /** @var \Drupal\consumers\Entity\ConsumerInterface $entity */
+    // Special handling for the secret field added by simple_oauth,
+    // make sure that it is not hashed again.
+    if ($entity->hasField('secret')) {
+      $entity->get('secret')->pre_hashed = TRUE;
+    }
+    parent::restore($entity);
+  }
+
+}

web/modules/consumers/src/Entity/Consumer.php

@@ -0,0 +1,274 @@
+<?php
+
+namespace Drupal\consumers\Entity;
+
+use Drupal\Core\Access\AccessException;
+use Drupal\Core\Entity\ContentEntityBase;
+use Drupal\Core\Entity\EntityChangedTrait;
+use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\Utility\Error;
+use Drupal\user\EntityOwnerTrait;
+
+/**
+ * Defines the Consumer entity.
+ *
+ * @ContentEntityType(
+ *   id = "consumer",
+ *   label = @Translation("Consumer"),
+ *   label_collection = @Translation("Consumers"),
+ *   label_singular = @Translation("consumer"),
+ *   label_plural = @Translation("consumers"),
+ *   handlers = {
+ *     "list_builder" = "Drupal\consumers\ConsumerListBuilder",
+ *     "form" = {
+ *       "default" = "Drupal\consumers\Entity\Form\ConsumerForm",
+ *       "add" = "Drupal\consumers\Entity\Form\ConsumerForm",
+ *       "edit" = "Drupal\consumers\Entity\Form\ConsumerForm",
+ *       "delete" = "Drupal\Core\Entity\ContentEntityDeleteForm",
+ *       "make-default" = "Drupal\consumers\Entity\Form\MakeDefaultForm",
+ *     },
+ *     "route_provider" = {
+ *       "html" = "Drupal\consumers\Entity\Routing\HtmlRouteProvider",
+ *     },
+ *     "views_data" = "\Drupal\views\EntityViewsData",
+ *     "access" = "Drupal\consumers\AccessControlHandler",
+ *     "storage" = "Drupal\consumers\ConsumerStorage",
+ *   },
+ *   base_table = "consumer",
+ *   data_table = "consumer_field_data",
+ *   translatable = TRUE,
+ *   admin_permission = "administer consumer entities",
+ *   entity_keys = {
+ *     "id" = "id",
+ *     "label" = "label",
+ *     "uuid" = "uuid",
+ *     "langcode" = "langcode",
+ *     "owner" = "owner_id",
+ *   },
+ *   links = {
+ *     "canonical" = "/admin/config/services/consumer/{consumer}",
+ *     "collection" = "/admin/config/services/consumer",
+ *     "add-form" = "/admin/config/services/consumer/add",
+ *     "edit-form" = "/admin/config/services/consumer/{consumer}/edit",
+ *     "delete-form" = "/admin/config/services/consumer/{consumer}/delete",
+ *     "make-default-form" = "/admin/config/services/consumer/{consumer}/make-default",
+ *   }
+ * )
+ */
+class Consumer extends ContentEntityBase implements ConsumerInterface {
+
+  use EntityChangedTrait;
+  use EntityOwnerTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function preSave(EntityStorageInterface $storage) {
+    parent::preSave($storage);
+    $was_not_default = is_null($this->original)
+      || !$this->original->get('is_default')->value;
+    if ($this->get('is_default')->value && $was_not_default) {
+      // If we are making this the new default consumer.
+      try {
+        $this->removeDefaultConsumerFlags();
+      }
+      catch (AccessException $exception) {
+        // Backwards compatibility of error logging. See
+        // https://www.drupal.org/node/2932520. This can be removed when we no
+        // longer support Drupal > 10.1.
+        if (version_compare(\Drupal::VERSION, '10.1', '>=')) {
+          $logger = \Drupal::logger('consumers');
+          Error::logException($logger, $exception);
+        }
+        else {
+          // @phpstan-ignore-next-line
+          watchdog_exception('consumers', $exception);
+        }
+
+        \Drupal::messenger()->addError($exception->getMessage());
+        $this->set('is_default', FALSE);
+      }
+    }
+
+    foreach (array_keys($this->getTranslationLanguages()) as $langcode) {
+      $translation = $this->getTranslation($langcode);
+
+      // If no owner has been set explicitly, make the anonymous user the owner.
+      if (!$translation->get('owner_id')->entity) {
+        $translation->set('owner_id', 0);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
+    $fields = parent::baseFieldDefinitions($entity_type);
+    $fields += static::ownerBaseFieldDefinitions($entity_type);
+
+    // Prepare args for translatable markup.
+    $args['@label'] = $entity_type->getSingularLabel();
+
+    $fields['client_id'] = BaseFieldDefinition::create('string')
+      ->setLabel(new TranslatableMarkup('Client ID'))
+      ->setDescription(new TranslatableMarkup('The client ID associated with this @label. This is an arbitrary unique field, like a machine name.', $args))
+      ->setRequired(TRUE)
+      ->setRevisionable(TRUE)
+      ->addConstraint('UniqueField')
+      ->setSetting('max_length', 255)
+      ->setDisplayOptions('form', [
+        'type' => 'string_textfield',
+        'weight' => -4,
+      ])
+      ->setDisplayConfigurable('form', TRUE);
+    $fields['label'] = BaseFieldDefinition::create('string')
+      ->setLabel(new TranslatableMarkup('Label'))
+      ->setDescription(new TranslatableMarkup('The @label label.', $args))
+      ->setRequired(TRUE)
+      ->setTranslatable(TRUE)
+      ->setRevisionable(TRUE)
+      ->setSetting('max_length', 255)
+      ->setDisplayOptions('view', [
+        'label' => 'hidden',
+        'type' => 'string',
+        'weight' => -5,
+      ])
+      ->setDisplayOptions('form', [
+        'type' => 'string_textfield',
+        'weight' => -5,
+      ])
+      ->setDisplayConfigurable('form', TRUE);
+    $fields['description'] = BaseFieldDefinition::create('string_long')
+      ->setLabel(t('Description'))
+      ->setDescription(t('A description of the @label. This text will be shown to the users to authorize sharing their data to create an access token.', $args))
+      ->setTranslatable(TRUE)
+      ->setDisplayOptions('view', [
+        'label' => 'hidden',
+        'type' => 'string',
+        'weight' => 0,
+      ])
+      ->setDisplayConfigurable('view', TRUE)
+      ->setDisplayOptions('form', [
+        'type' => 'string_textfield',
+        'weight' => 0,
+      ])
+      ->setDisplayConfigurable('form', TRUE);
+
+    $fields['image'] = BaseFieldDefinition::create('image')
+      ->setLabel(t('Logo'))
+      ->setDescription(t('Logo of the @label.', $args))
+      ->setRevisionable(TRUE)
+      ->setTranslatable(TRUE)
+      ->setDisplayOptions('view', [
+        'label' => 'hidden',
+        'type' => 'image',
+        'weight' => -3,
+      ])
+      ->setDisplayOptions('form', [
+        'type' => 'image_image',
+        'weight' => -3,
+        'settings' => [
+          'preview_image_style' => 'thumbnail',
+          'progress_indicator' => 'throbber',
+        ],
+      ])
+      ->setDisplayConfigurable('form', TRUE)
+      ->setDisplayConfigurable('view', TRUE);
+
+    $fields['third_party'] = BaseFieldDefinition::create('boolean')
+      ->setLabel(new TranslatableMarkup('Is this @label 3rd party?', $args))
+      ->setDescription(new TranslatableMarkup('Mark this if the organization behind this @label is not the same as the one behind the Drupal API.', $args))
+      ->setDisplayOptions('view', [
+        'label' => 'inline',
+        'type' => 'boolean',
+        'weight' => 4,
+      ])
+      ->setDisplayOptions('form', [
+        'weight' => 4,
+      ])
+      ->setRevisionable(TRUE)
+      ->setTranslatable(TRUE)
+      ->setDefaultValue(TRUE);
+
+    $fields['is_default'] = BaseFieldDefinition::create('boolean')
+      ->setLabel(new TranslatableMarkup('Is this the default @label?', $args))
+      ->setDescription(new TranslatableMarkup('There can only be one default @label. Mark this to use this @label when none other applies.', $args))
+      ->setDisplayOptions('view', [
+        'label' => 'inline',
+        'type' => 'boolean',
+        'weight' => 4,
+      ])
+      ->setDisplayOptions('form', [
+        'weight' => 4,
+      ])
+      ->setRevisionable(TRUE)
+      ->setTranslatable(TRUE)
+      ->setDefaultValue(FALSE);
+
+    return $fields;
+  }
+
+  /**
+   * Removes the is_default flag from other consumers.
+   *
+   * @throws \Drupal\Component\Plugin\Exception\PluginException
+   * @throws \Drupal\Core\Access\AccessException
+   */
+  protected function removeDefaultConsumerFlags() {
+    // Find the old defaults.
+    $entity_storage = $this->entityTypeManager()
+      ->getStorage($this->getEntityTypeId());
+    $entity_ids = $entity_storage
+      ->getQuery()
+      ->accessCheck(TRUE)
+      ->condition('is_default', TRUE)
+      ->condition('id', $this->id(), '!=')
+      ->execute();
+    $entity_ids = $entity_ids ? array_values($entity_ids) : [];
+    if (empty($entity_ids)) {
+      $default_entities = [];
+    }
+    else {
+      $default_entities = $entity_storage->loadMultiple($entity_ids);
+      $default_entities = array_map(
+        static::setDefaultTo(FALSE),
+        $default_entities
+      );
+      $invalid_entities = array_filter($default_entities, function (ConsumerInterface $consumer) {
+        return !$consumer->access('update', NULL, TRUE)->isAllowed();
+      });
+      if (count($invalid_entities)) {
+        throw new AccessException('Unable to change the current default consumer. Permission denied.');
+      }
+    }
+    array_map([$entity_storage, 'save'], $default_entities);
+  }
+
+  /**
+   * Gets closure that will set is_default to the selected value for an entity.
+   *
+   * @param bool $value
+   *   The final value of the "is_default" field.
+   *
+   * @return \Closure
+   *   The closure that will set the "is_default" field to the selected value.
+   */
+  protected static function setDefaultTo($value) {
+    return function (ConsumerInterface $consumer) use ($value) {
+      $consumer->set('is_default', $value);
+      return $consumer;
+    };
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getClientId(): string {
+    return $this->get('client_id')->value;
+  }
+
+}

web/modules/consumers/src/Entity/ConsumerInterface.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Drupal\consumers\Entity;
+
+use Drupal\Core\Entity\ContentEntityInterface;
+use Drupal\user\EntityOwnerInterface;
+
+/**
+ * Provides an interface defining a consumer entity.
+ */
+interface ConsumerInterface extends ContentEntityInterface, EntityOwnerInterface {
+
+  /**
+   * Gets the client ID.
+   *
+   * @return string
+   *   The client ID.
+   */
+  public function getClientId(): string;
+
+}

web/modules/consumers/src/Entity/Form/ConsumerForm.php

@@ -0,0 +1,70 @@
+<?php
+
+namespace Drupal\consumers\Entity\Form;
+
+use Drupal\Component\Utility\Crypt;
+use Drupal\Core\Entity\ContentEntityForm;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Form controller for Consumer edit forms.
+ */
+class ConsumerForm extends ContentEntityForm {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function form(array $form, FormStateInterface $form_state) {
+    $form = parent::form($form, $form_state);
+
+    $form['is_default']['#access'] = FALSE;
+    $form['client_id']['generate'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Generate random Client ID'),
+      '#limit_validation_errors' => [$form['client_id']['widget']['#parents']],
+      '#attributes' => [
+        'class' => [
+          'button--small',
+        ],
+      ],
+      '#ajax' => [
+        'callback' => [$this, 'generateClientId'],
+        'disable-refocus' => TRUE,
+        'wrapper' => 'edit-client-id-wrapper',
+      ],
+    ];
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function save(array $form, FormStateInterface $form_state) {
+    $status = $this->entity->save();
+    $label = $this->entity->label();
+    $args = [
+      '%label' => $label,
+      '@type' => $this->entity->getEntityType()->getLabel(),
+    ];
+
+    switch ($status) {
+      case SAVED_NEW:
+        $this->messenger()->addMessage($this->t('Created the %label @type.', $args));
+        break;
+
+      default:
+        $this->messenger()->addMessage($this->t('Saved the %label @type.', $args));
+    }
+    $form_state->setRedirect('entity.consumer.collection');
+    return $status;
+  }
+
+  /**
+   * AJAX callback that generates the client ID.
+   */
+  public function generateClientId(array &$form, FormStateInterface $form_state): array {
+    $form['client_id']['widget'][0]['value']['#value'] = Crypt::randomBytesBase64();
+    return $form['client_id'];
+  }
+
+}

web/modules/consumers/src/Entity/Form/MakeDefaultForm.php

@@ -0,0 +1,64 @@
+<?php
+
+namespace Drupal\consumers\Entity\Form;
+
+use Drupal\Core\Entity\ContentEntityConfirmFormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+
+/**
+ * Form controller for the Consumer make default form.
+ *
+ * @ingroup consumers
+ */
+class MakeDefaultForm extends ContentEntityConfirmFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getQuestion() {
+    return $this->t('Are you sure you want to make %consumer the default @label?', [
+      '%consumer' => $this->entity->label(),
+      '@label' => $this->entity->getEntityType()->getSingularLabel(),
+    ]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    return $this->t('The @label currently marked as default will lose this property, since there can only be one default @label. This may break current assumptions in existing client-side applications.', [
+      '@label' => $this->entity->getEntityType()->getSingularLabel(),
+    ]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCancelUrl() {
+    return Url::fromRoute('entity.consumer.collection');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getConfirmText() {
+    return $this->t('Make Default');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    // Make the submitted entity the new default.
+    /** @var \Drupal\consumers\Entity\ConsumerInterface $entity */
+    $entity = $this->getEntity();
+    if ($entity->get('is_default')->value) {
+      // This is already the default. Do nothing.
+      return;
+    }
+    $entity->set('is_default', TRUE);
+    $entity->save();
+  }
+
+}

web/modules/consumers/src/Entity/Routing/HtmlRouteProvider.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\consumers\Entity\Routing;
+
+use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Entity\Routing\DefaultHtmlRouteProvider;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Provides HTML routes for the Consumer entity.
+ */
+class HtmlRouteProvider extends DefaultHtmlRouteProvider {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getRoutes(EntityTypeInterface $entity_type) {
+    $collection = parent::getRoutes($entity_type);
+    $route = new Route($entity_type->getLinkTemplate('make-default-form'));
+    $route
+      ->addDefaults([
+        '_entity_form' => 'consumer.make-default',
+        '_title_callback' => '\Drupal\Core\Entity\Controller\EntityController::title',
+      ])
+      ->setRequirement('_entity_access', 'consumer.update')
+      ->setOption('parameters', ['consumer' => ['type' => 'entity:consumer']]);
+    $collection->add(
+      'entity.consumer.make_default_form',
+      $route
+    );
+    return $collection;
+  }
+
+}

web/modules/consumers/src/EventSubscriber/ConsumerVaryEventSubscriber.php

@@ -0,0 +1,75 @@
+<?php
+
+namespace Drupal\consumers\EventSubscriber;
+
+use Drupal\consumers\MissingConsumer;
+use Drupal\consumers\Negotiator;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+use Symfony\Component\HttpKernel\Event\ResponseEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
+
+/**
+ * Vary header by consumer.
+ */
+class ConsumerVaryEventSubscriber implements EventSubscriberInterface {
+
+  /**
+   * The consumer id header key.
+   *
+   * @var string
+   */
+  const CONSUMER_ID_HEADER = 'X-Consumer-ID';
+
+  /**
+   * The consumer negotiator.
+   *
+   * @var \Drupal\consumers\Negotiator
+   */
+  protected $negotiator;
+
+  /**
+   * ConsumerVaryEventSubscriber constructor.
+   *
+   * @param \Drupal\consumers\Negotiator $negotiator
+   *   The consumer negotiator.
+   */
+  public function __construct(Negotiator $negotiator) {
+    $this->negotiator = $negotiator;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents() {
+    return [
+      KernelEvents::RESPONSE => 'onRespond',
+    ];
+  }
+
+  /**
+   * React on response and set the Vary header.
+   */
+  public function onRespond(ResponseEvent $event) {
+    $response = $event->getResponse();
+
+    try {
+      $consumer = $this->negotiator->negotiateFromRequest($event->getRequest());
+    }
+    catch (MissingConsumer $e) {
+      // If there's no consumer in the header, and no default consumer then we
+      // don't need to add any Vary headers.
+      $consumer = FALSE;
+    }
+
+    if ($consumer) {
+      // Add consumer id to headers.
+      $response->headers->set(self::CONSUMER_ID_HEADER, $consumer->getClientId());
+
+      // Add consumer id to vary headers.
+      $vary_headers = $response->getVary();
+      $vary_headers[] = self::CONSUMER_ID_HEADER;
+      $response->setVary($vary_headers);
+    }
+  }
+
+}

web/modules/consumers/src/MissingConsumer.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Drupal\consumers;
+
+/**
+ * Exception thrown when a consumer is missing.
+ */
+class MissingConsumer extends \Exception {}

web/modules/consumers/src/Negotiator.php

@@ -0,0 +1,160 @@
+<?php
+
+namespace Drupal\consumers;
+
+use Drupal\Core\Entity\EntityStorageException;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Utility\Error;
+use Psr\Log\LoggerAwareTrait;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\RequestStack;
+
+/**
+ * Extracts the consumer information from the given context.
+ *
+ * @internal
+ */
+class Negotiator {
+
+  use LoggerAwareTrait;
+
+  /**
+   * Protected requestStack.
+   *
+   * @var \Symfony\Component\HttpFoundation\RequestStack
+   */
+  protected $requestStack;
+
+  /**
+   * The entity storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $storage;
+
+  /**
+   * The default consumer.
+   *
+   * @var \Drupal\consumers\Entity\ConsumerInterface
+   */
+  protected $defaultConsumer;
+
+  /**
+   * Instantiates a new Negotiator object.
+   */
+  public function __construct(RequestStack $request_stack, LoggerInterface $logger) {
+    $this->requestStack = $request_stack;
+    $this->logger = $logger;
+  }
+
+  /**
+   * Obtains the consumer from the request.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request.
+   *
+   * @return \Drupal\consumers\Entity\ConsumerInterface|null
+   *   The consumer.
+   *
+   * @throws \Drupal\consumers\MissingConsumer
+   */
+  protected function doNegotiateFromRequest(Request $request) {
+    // There are several ways to negotiate the consumer:
+    // 1. Via a custom header.
+    $consumer_id = $request->headers->get('X-Consumer-ID');
+    if (!$consumer_id) {
+      // 2. Via a query string parameter.
+      $consumer_id = $request->query->get('consumerId');
+      if (!$consumer_id && $request->query->has('_consumer_id')) {
+        $this->logger->warning('The "_consumer_id" query string parameter is deprecated and it will be removed in the next major version of the module, please use "consumerId" instead.');
+        $consumer_id = $request->query->get('_consumer_id');
+      }
+    }
+    if ($consumer_id) {
+      try {
+        $results = $this->storage->loadByProperties(['client_id' => $consumer_id]);
+        /** @var \Drupal\consumers\Entity\ConsumerInterface $consumer */
+        $consumer = !empty($results) ? reset($results) : $results;
+      }
+      catch (EntityStorageException $exception) {
+        // Backwards compatibility of error logging. See
+        // https://www.drupal.org/node/2932520. This can be removed when we no
+        // longer support Drupal > 10.1.
+        if (version_compare(\Drupal::VERSION, '10.1', '>=')) {
+          $logger = \Drupal::logger('consumers');
+          Error::logException($logger, $exception);
+        }
+        else {
+          // @phpstan-ignore-next-line
+          watchdog_exception('consumers', $exception);
+        }
+      }
+    }
+    if (empty($consumer)) {
+      $consumer = $this->loadDefaultConsumer();
+    }
+    return $consumer;
+  }
+
+  /**
+   * Obtains the consumer from the request.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request|null $request
+   *   The request object to inspect for a consumer. Set to NULL to use the
+   *   current request.
+   *
+   * @return \Drupal\consumers\Entity\ConsumerInterface|null
+   *   The consumer.
+   *
+   * @throws \Drupal\consumers\MissingConsumer
+   */
+  public function negotiateFromRequest(Request $request = NULL) {
+    // If the request is not provided, use the request from the stack.
+    $request = $request ? $request : $this->requestStack->getCurrentRequest();
+    $consumer = $this->doNegotiateFromRequest($request);
+    $request->attributes->set('consumer_id', $consumer->getClientId());
+    return $consumer;
+  }
+
+  /**
+   * Finds and loads the default consumer.
+   *
+   * @return \Drupal\consumers\Entity\ConsumerInterface
+   *   The consumer entity.
+   *
+   * @throws \Drupal\consumers\MissingConsumer
+   */
+  protected function loadDefaultConsumer() {
+    if (!empty($this->defaultConsumer)) {
+      return $this->defaultConsumer;
+    }
+
+    // Find the default consumer.
+    $results = $this->storage->getQuery()
+      ->accessCheck(TRUE)
+      ->condition('is_default', TRUE)
+      ->execute();
+    $consumer_id = reset($results);
+    if (!$consumer_id) {
+      // Throw if there is no default consumer.
+      throw new MissingConsumer('Unable to find the default consumer.');
+    }
+    $this->defaultConsumer = $this->storage->load($consumer_id);
+
+    return $this->defaultConsumer;
+  }
+
+  /**
+   * Sets the storage from the entity type manager.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   *
+   * @throws \Drupal\Component\Plugin\Exception\PluginException
+   */
+  public function setEntityStorage(EntityTypeManagerInterface $entity_type_manager) {
+    $this->storage = $entity_type_manager->getStorage('consumer');
+  }
+
+}

web/modules/consumers/src/Plugin/Menu/ConsumersCollectionLink.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace Drupal\consumers\Plugin\Menu;
+
+use Drupal\Core\Menu\MenuLinkDefault;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * A menu link to Consumers collection page.
+ */
+class ConsumersCollectionLink extends MenuLinkDefault {
+  use StringTranslationTrait;
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    $instance = parent::create($container, $configuration, $plugin_id, $plugin_definition);
+    $instance->entityTypeManager = $container->get('entity_type.manager');
+    $instance->setStringTranslation($container->get('string_translation'));
+    return $instance;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTitle() {
+    return $this->entityTypeManager->getDefinition('consumer')->getCollectionLabel();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    return $this->t('Register and configure the decoupled @label to your API.', [
+      '@label' => $this->entityTypeManager->getDefinition('consumer')->getPluralLabel(),
+    ]);
+  }
+
+}

web/modules/consumers/src/Plugin/Menu/LocalAction/AddConsumerAction.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Drupal\consumers\Plugin\Menu\LocalAction;
+
+use Drupal\Core\Menu\LocalActionDefault;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Provides a local action for adding a consumer.
+ */
+class AddConsumerAction extends LocalActionDefault {
+  use StringTranslationTrait;
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    $instance = parent::create($container, $configuration, $plugin_id, $plugin_definition);
+    $instance->entityTypeManager = $container->get('entity_type.manager');
+    $instance->setStringTranslation($container->get('string_translation'));
+    return $instance;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTitle(Request $request = NULL) {
+    return $this->t('Add @label', [
+      '@label' => $this->entityTypeManager->getDefinition('consumer')->getLabel(),
+    ]);
+  }
+
+}