Implements #21

This is a breaking change.

Changelog:
- Redis is now mandatory and enabled by default
- Added Sentinel, Standalone and Cluster support
- Standalone mode with sidecar is used by default
  - If no host(s) are configured, a redis sidecar is injected into the deployment
  - No extra configuration needed
  - This is intended for development and does not scale.
- Helm values have changed, see README.md:
  - `redis.host` has been renamed to `redis.hosts` and expects a list of strings with the following pattern: <localhost:6379> (needed for sentinel and cluster modes)
  - `redis.port` has been removed, see `redis.hosts`

julian.baeume authored 3 years ago and david.bauer committed 2 years ago

hopefully helps to better understand the big picture.

it's just a simple switch, but we want to have it documented for completeness.

describe a little better what this service is supposed to do and how
it plays along the other parts of the stack.