feat(rest): Add /health endpoint to rest api

[alrevuelta]

Problem

nwaku has a bunch of things happening under the hood that are required for the node to work properly. Some of them are:

• healthy amount of peers
• rln in sync to the latest head
• all services mounted and running

However we don't have a /health endpoint that returns such information. We need some kind of readyness probe.

Suggested solution

• Add new /health endpoint in the rest api that returns true if the node is ready and false if not. By now its ok to just check if rln is in sync with the latest head. Similar to this

[NagyZoltanPeter]

Weekly Update

• achieved: Feature /health endpoint added. PR merged: feat: Rest endoint /health for rln #2011