Add API health check

**Is your feature request related to a problem? Please describe.**
add an API health check to return appropriate readiness status for the DS API service.

**Describe the solution you'd like**
As a consumer of the DS API, I would want to check the API service status which would include the service health and if the service can successfully call a downstream resource. At a high level, the API health check should include:
* application level status
* HTTP protocol and /healthz endpoint
* appropriate error details for failures
* Follow k8s readinessProbe best practices [here](https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/)