in FormLoginHandler, the DEFAULT_RETURN_URL_PARAM indicatees the sessions attribute it will be retrieved from, not the form attribute
@@ -44,7 +44,7 @@ public interface FormLoginHandler extends Handler<RoutingContext> {
String DEFAULT_PASSWORD_PARAM = "password";
/**
- * The default value of the form attribute which will contain the return url
+ * The default value of the session attribute which will contain the return url
*/
String DEFAULT_RETURN_URL_PARAM = "return_url";
