No way to specify Redis password

The only possible redis config are host and port ([src/rest/auth.ts#L43](https://github.com/atlassian/nucleus/blob/master/src/rest/auth.ts#L43)), but this is only a small subset of possible options (https://www.npmjs.com/package/connect-redis). In my specific case I need to connect using a password, but setting db and prefix can also be useful.

Start with the Redis configuration in src/rest/auth.ts at line 43, then compare the supported options with the connect-redis documentation linked in the issue. The change is done when Redis connections can be configured with a password, while also allowing options such as db and prefix.

Written by the indexing model from the issue text.