+ * The authentication providers, like 'cookie' and 'basic_auth'.
+ *
+ * @var string[]
+ */
+ protected $authenticationProviderIds;
+
+ /**
+ * The authentication providers' modules, keyed by provider ID.
+ *
+ * Authentication providers like 'cookie' and 'basic_auth' are the array
+ * keys. The array values are the module names, e.g.:
+ * @code
+ * ['cookie' => 'user', 'basic_auth' => 'basic_auth']
+ * @endcode
+ *
+ * @deprecated as of 8.4.x, will be removed in before Drupal 9.0.0, see
+ * https://www.drupal.org/node/2825204.