Introduce HealthService

[raphael-goetz]

For a better Kubernetes integration a Health Service should be introduced.

Implementation should be based on tonic:
https://github.com/hyperium/tonic/blob/master/tonic-health/src/generated/grpc_health_v1.rs

Ref: https://github.com/code0-tech/sagittarius/blob/main/app/grpc/health_handler.rb