Consider having a built-in adapter for Prometheus

[ashwinuae]

While Cachet currently only concerns itself with displaying statuses (and maintenance messages) for components, these are still to be created/updated manually via the Dashboard (or API). Of course there is the possibility of integrating with Oh Dear, but in the interest of presenting a truly open-source solution that kinda 'closes the loop' it'd be great to have a built-in integration with Prometheus.

At least in the past with v2, there was reasonable demand for such a solution, as elicited by the following 3rd party adapters (which unfortunately are not maintained anymore, and probably don't play well with v3):

• https://github.com/gregdhill/prometheus-cachet
• https://github.com/oxyno-zeta/prometheus-cachethq

As far as I can see, this mostly revolves around having a translator for the webhook events from Prometheus Alertmanager, some way to map the individual entities to components, and of course resolving incidents when they stop firing.

Looking forward to further discussions on this matter!