Add username support for Sentinel Configuration

[vikasgarghb]

In order to use authentication on sentinel using ACLs there needs to be support added on sentinel configuration for Lettuce. Similar to what has been done on spring-boot: spring-projects/spring-boot@36382e5

[mourezwell]

is there a plan to expand this enhancement to spring-boot, in deed org.springframework.boot.autoconfigure.data.redis.RedisProperties does not support sentinel username yet,
so does org.springframework.boot.autoconfigure.data.redis.RedisConnectionConfiguration can't set SentinelUsernma you've just added here ?