Hyperion: Provide data on what Hyperion is doing

For external monitoring services it is useful to know some data about what is happening on the beamline, specifically:
* Current visit
* Baton holder

And some history of when these changed. GDA pushed this information to a `redis` database sitting on the control machine (https://jira.diamond.ac.uk/browse/I04_1-737). Hyperion could do the same but should probably use something on the K8s cluster.

Ultimately we may also want to put sensitive data in there, like file names, so will also need some authentication.

## Acceptance Criteria
- Hyperion pushes the above data into an externally readable service