Implement gRPC server healthcheck

[flavienbwk]

Implementing state-of-the-art gRPC server healthcheck in the server container.

Resources :

• https://stackoverflow.com/questions/56984565/python-grpc-health-check
• https://github.com/grpc-ecosystem/grpc-health-probe
• https://cloud.google.com/blog/topics/developers-practitioners/health-checking-your-grpc-servers-gke