Non-HTTP based example application

### What problem are you trying to solve?

Emojivoto and the books app are great examples. Unfortunately, they're exclusively HTTP based and use many kubernetes best practices. With features on the horizon like TCP mTLS, there should be an example application that actually uses this functionality which can be used for testing and tutorials.

This application should use a client speaks first protocol that is not HTTP.

### How should the problem be solved?

Extend emojivoto to use redis as a cache for votes and emojis. This should probably be an optional component, perhaps added via configuration and a kustomize addition.

### Any alternatives you've considered?

There are lots of other ways to solve this that might be better, please take the above as simply a suggestion.

Start by reviewing the emojivoto example and its Kubernetes configuration, then compare how the books app is structured. Investigate whether Redis can be introduced as an optional cache through configuration and a kustomize addition. Done should include a non-HTTP, client-speaks-first example suitable for exercising TCP mTLS in testing or tutorials.

Written by the indexing model from the issue text.