adds topic controllers

src/Appwrite/Extend/Exception.php

@@ -217,6 +217,9 @@ class Exception extends \Exception
     public const PROVIDER_NOT_FOUND                 = 'provider_not_found';
     public const PROVIDER_INCORRECT_TYPE            = 'provider_incorrect_type';
 
+    /** Topic */
+    public const TOPIC_NOT_FOUND                    = 'topic_not_found';
+
     protected $type = '';
     protected $errors = [];
 

src/Appwrite/Utopia/Database/Validator/Queries/Topics.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Appwrite\Utopia\Database\Validator\Queries;
+
+class Topics extends Base
+{
+    public const ALLOWED_ATTRIBUTES = [
+        'name',
+        'description',
+    ];
+
+    /**
+     * Expression constructor
+     *
+     */
+    public function __construct()
+    {
+        parent::__construct('topics', self::ALLOWED_ATTRIBUTES);
+    }
+}