[keycloak-user] Return 503 (Service Unvailable) instead of 404 (File Not found) during keycloak server restarts

Hello group, the undertow servlet-container is started pretty early during the startup of the wildfly application server. However the initialization of the keycloak server application might take a while to complete. Within this period requests that are sent to the keycloak endpoints result in responses with HTTP Status Code 404. Is it possible to configure undertow to return a HTTP Status Code 503 (Service Unvailable) until the keycloak application startup has completed? This would ease configuring load-balancers and to avoid showing a 404 to users during server restarts. Cheers, Thomas