update PHPDoc

src/Model/Notification.php

@@ -14,7 +14,10 @@ use Psr\Log\LoggerInterface;
 
 /**
  * Model for an entry in the notify table
- * - Including additional calculated properties
+ * - Including additional, calculated properties
+ *
+ * Is used either for frontend interactions or for API-based interaction
+ * @see https://github.com/friendica/friendica/blob/develop/doc/API-Entities.md#notification
  *
  * @property string  hash
  * @property integer type

src/Object/Notification/Introduction.php

@@ -2,6 +2,9 @@
 
 namespace Friendica\Object\Notification;
 
+/**
+ * A view-only object for printing introduction notifications to the frontend
+ */
 class Introduction implements \JsonSerializable
 {
 	/** @var string */

src/Object/Notification/Notification.php

@@ -2,6 +2,9 @@
 
 namespace Friendica\Object\Notification;
 
+/**
+ * A view-only object for printing item notifications to the frontend
+ */
 class Notification implements \JsonSerializable
 {
 	const SYSTEM   = 'system';