Create Appwrite Query Validator

The Appwrite Query Validator checks if the cursor value is a valid UID.
This is different than the cursor value in utopia-php/database because
the value in the database layer is expected to be a document.

src/Appwrite/Utopia/Database/Validator/Query.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Appwrite\Utopia\Database\Validator;
+
+use Utopia\Database\Validator\UID;
+use Utopia\Database\Validator\Query as QueryValidator;
+
+class Query extends QueryValidator
+{
+    protected function isValidCursor($cursor): bool
+    {
+        $validator = new UID();
+
+        if ($validator->isValid($cursor)) {
+            return true;
+        }
+
+        $this->message = 'Invalid cursor: ' . $validator->getDescription();
+        return false;
+    }
+}