Agregado método __toString

Entity/OAuthClient.php

@@ -18,10 +18,15 @@ class OAuthClient extends BaseClient
      */
     protected $id;
 
-    
+
     public function __construct()
     {
         parent::__construct();
     }
 
+    public function __toString()
+    {
+        return strval($this->id);
+    }
+
 }