Add authentication to caching/persistence stores

As already mentioned in discussions some time ago and retriggered by a user on talk recently, we need to think about adding authentication for caching/persistence stores.

`redis`, `redis-sentinel`, `etcd`, `nats-js` at least share the availability for a pwd, some also require a user.

This would make it _relatively_ easy to define common local/global envvars for authentication.

@micbar @aduffeck fyi

No files, tests, or entry points are named. Start by locating the configuration and connection entry points for redis, redis-sentinel, etcd, and nats-js, then review how local and global environment variables are defined. Done means the relevant stores support password and, where required, user authentication through a consistent configuration approach.

Written by the indexing model from the issue text.