Added serverError exception

src/Exception/OAuthServerException.php

@@ -163,6 +163,18 @@ class OAuthServerException extends \Exception
         return new static('The user credentials were incorrect.', 'invalid_credentials', 401);
     }
 
+    /**
+     * Server error
+     *
+     * @param $hint
+     *
+     * @return static
+     */
+    public static function serverError($hint)
+    {
+        return new static('\'The authorization server encountered an unexpected condition which prevented it from fulfilling the request.', 'server_errror', 500, $hint);
+    }
+
     /**
      * @return string
      */