[feature/oauth] Update interface appropriately

PHPBB3-11673

phpBB/phpbb/auth/provider/oauth/service/interface.php

@@ -49,6 +49,13 @@ interface phpbb_auth_provider_oauth_service_interface
 	*/
 	public function get_service_credentials();
 
+	/**
+	* Returns the results of the authentication in json format
+	*
+	* @return	type	The results of the authentication action in json format.
+	*/
+	public function perform_auth_login();
+
 	/**
 	* Sets the external library service provider
 	*