Add a /health that tests connection to the various databases

[CharlesNepote]

In Folksonomy Engine API we have either:

• / leading to answer { "message": "Hello folksonomy World! Tip: open /docs for documentation" }
• /ping which answers { "ping": "pong @ 2023-09-26 07:49:10.842300" }

See:

• https://api.folksonomy.openfoodfacts.org/docs
• https://github.com/openfoodfacts/folksonomy_api/blob/main/folksonomy/api.py

[alexgarel]

It's even better to add a /health that tests connection to the various databases. Like for robotoff https://robotoff.openfoodfacts.org/api/v1/health

[teolemon]

Duplicate of #67