Hot-reload beamium scrapers

[sebgl]

It would be nice to have a 'hot-reload' feature so that we can add/remove scrapers without restarting beamium.

Our use-case:
Beamium is installed on every machine, then we specialize some machines with specific services. All of our services expose a '/metrics' endpoint to be scraped by beamium. When we add/modify/remove a service, we have to restart beamium so that it can take the new scrapers list into consideration.
I guess we could call the hot-reload of beamium every time we deploy a service; most time the reload would be useless (same services, same scrapers), meaning it has to be idempotent.