Add authentication mechanism example

[JonBau]

The service APIs require authentication and we should also add an example for that.

A first approach could be based on external authentication in the k8s ingress controller together with an identity provider, e.g. nginx together with keycloack (https://kubernetes.github.io/ingress-nginx/examples/auth/external-auth/)

However, this might not be possible on all clusters, in particular on managed k8s instances.
An alternative solution could be based on additional reverse proxys or api gateways deployed alongside the services in order to handle authentication and authorization.

[m-mirz]

Shovon will be looking into a minimal setup including Grafana as an example service and keycloak.
This is related to PR #11