Health check endpoint

Often in deployments, a health check endpoint is required for the CI/CD to ensure that the service has deployed properly. At least [aws requires it in load balancers][1].

In SCIO, any endpoint can serve as a healthcheck, for eg: `/api/?format=json` as long as it is running unauthenticated.
With authentication enabled, all endpoints will throw `401` without a token. There are two possible solutions:

1. Implement a `/healthcheck` endpoint in SCIO that gives 200 after checking basic db connection etc
2. Goto AWS -> Target Group (under load balancing) -> Health checks (tab) -> Edit -> Advanced health check settings -> Success codes -> add `401`

[1]: https://docs.aws.amazon.com/elasticloadbalancing/latest/network/target-group-health-checks.html