WIP redis sentinel

[stgrace]

Description of feature

Support for redis sentinel

Additional information

So far added redis_host has a list of tuples, just like in arq.
Attempted to use a Union of tuples and str, but when I did it always parsed the conf through the environment as a string.

TODO

• Change stackl-redis entrypoint for sentinel (sentinel.conf must be writeable, so the config mounted from a cm cannot be used directly. Best to probably cp initial conf to empty-dir volume and use that conf, so stackl-redis can write to it. See how bitnami does it)
• Add connection to multiple redis for stackl-core (datastore and queue).
• Fix Union issue for redis_hosts config
• Run tests to see if data is not lost when failover happens