feat: add notifications inbox for actors

closes #215

app/Models/NotificationModel.php

@@ -0,0 +1,47 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright  2021 Ad Aures
+ * @license    https://www.gnu.org/licenses/agpl-3.0.en.html AGPL3
+ * @link       https://castopod.org/
+ */
+
+namespace App\Models;
+
+use App\Entities\Notification;
+use Michalsn\Uuid\UuidModel;
+
+class NotificationModel extends UuidModel
+{
+    /**
+     * @var string
+     */
+    protected $table = 'notifications';
+
+    /**
+     * @var string
+     */
+    protected $primaryKey = 'id';
+
+    /**
+     * @var string
+     */
+    protected $returnType = Notification::class;
+
+    /**
+     * @var bool
+     */
+    protected $useTimestamps = true;
+
+    /**
+     * @var string[]
+     */
+    protected $uuidFields = ['post_id', 'activity_id'];
+
+    /**
+     * @var string[]
+     */
+    protected $allowedFields = ['read_at'];
+}