Add "username" setting support to Sentinel mode

[georgelupu]

Feature Request

Add "setSentinelUsername" method to Sentinel mode

Is your feature request related to a problem? Please describe

Latest Redis (6+) servers have ACL support which allows us to have in the database other users than the "default" one, but the current Lettuce client driver implementation does not allow to provide the "username" under RedisSentinelConfiguration class. As result only the "default" db user can be used with the Lettuce driver in order to connect to Sentinel - which is a concern for DBOps folks who do not want to share "default" root/admin account with the application developers.

Describe the solution you'd like

Today, we can only provide setSentinelPassword config in RedisSentinelConfiguration class. Please add "setSentinelUsername" method support as well. Thank you!

Describe alternatives you've considered

No alternatives are available at the moment except using the "default" redis db user for connecting to Sentinel.