Expose health status as prometheus metric

[rachid-o]

It would be nice if we can monitor on (at least) the overall status as given in the field status in the response of /actuator/health. For our monitoring/alerting it would be very convenient if this status is part of /actuator/prometheus. I see that it isn’t yet included in axon server 4.5. Can this be included?

Please let me know what the possibilities and potential time lines could be. If you can confirm that this request would be included in axon server, I'm willing to see if I can create a pull request myself.