Implemented oauth session revocation notification.

Reworked webhooks notifications constructors

common/notifications/NotificationInterface.php

@@ -0,0 +1,12 @@
+<?php
+declare(strict_types=1);
+
+namespace common\notifications;
+
+interface NotificationInterface {
+
+    public static function getType(): string;
+
+    public function getPayloads(): array;
+
+}