[feature/oauth] Add method to return necessary data for auth_link

PHPBB3-11673

phpBB/phpbb/auth/provider/base.php

@@ -62,6 +62,14 @@ abstract class phpbb_auth_provider_base implements phpbb_auth_provider_interface
 		return;
 	}
 
+	/**
+	* {@inheritdoc}
+	*/
+	public function get_auth_link_data()
+	{
+		return;
+	}
+
 	/**
 	* {@inheritdoc}
 	*/