docs(auth): update OCP\IApacheBackend interface documentation

lib/public/Authentication/IApacheBackend.php

@@ -5,36 +5,44 @@
  * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
  * SPDX-License-Identifier: AGPL-3.0-only
  */
-// use OCP namespace for all classes that are considered public.
-// This means that they should be used by apps instead of the internal Nextcloud classes
 
 namespace OCP\Authentication;
 
 /**
- * Interface IApacheBackend
+ * Contract for user backends that integrate authentication performed outside
+ * of Nextcloud.
+ *
+ * Typical implementations integrate with web-server authentication modules,
+ * reverse proxies, or other external authentication services. Implementations
+ * include the user_saml and user_oidc apps.
+ *
+ * The interface name is historical and is retained for backwards
+ * compatibility; it is not limited to Apache.
  *
  * @since 6.0.0
  */
 interface IApacheBackend {
 	/**
-	 * In case the user has been authenticated by a module true is returned.
+	 * Whether the backend's external authentication mechanism considers the
+	 * current user logged in.
 	 *
-	 * @return bool whether the module reports a user as currently logged in.
 	 * @since 6.0.0
 	 */
 	public function isSessionActive(): bool;
 
 	/**
-	 * Gets the current logout URL
+	 * Returns the URL to use when logging out of this backend's external
+	 * authentication flow.
 	 *
 	 * @return non-empty-string
 	 * @since 12.0.3
 	 */
 	public function getLogoutUrl(): string;
 
 	/**
-	 * Return the id of the current user
-	 * @return string
+	 * Returns the ID of the Nextcloud user corresponding to the externally
+	 * authenticated user.
+	 *
 	 * @since 6.0.0
 	 */
 	public function getCurrentUserId(): string;