Add more information for healthcheck

[yacine-1]

It took me a long time to detect that the database connection was broken while frontend was working fine and the argocd deployment was healthy.

As mentioned in #153, I need a health endpoint to check if the backend and the database connection are ok (and optionally the version tag) without authentication.

When connected, api/_health endpoint returns "{}" but this information is not enough.

The documentation is not clear about this...