frontend: Prevent multiple errors when service is not available

Similar to what we did for the connection in general, where there's a middleman checking if there's connection before proceding with a backend request, we could have a middleman checking if the specific service used is online.
This would prevent errors where a service is not running and multiple sequencial error notifications are pushed.

This check should be done *after* the general backend check, so we don't have an infinite of "service down" notifications when the connection is dropped.

We could do this using a "registration" endpoint for the service, and take the opportunitty to use this together with the helper to show information regarding each service.