salt module - redis - Adding multiples instances in minion conf

Is your feature request related to a problem? Please describe.
I have an host with several redis instances, the issue is that apparently we can set only a redis instance in minion configuration.

Describe the solution you'd like
Solution can be add multiple instances with a tag like that:

instance_1:
  redis.host: 'salt'
  redis.port: 6379
  redis.db: 0
  redis.password: XXX
instance_2:
  redis.host: 'salt'
  redis.port: 6380
  redis.db: 0
  redis.password: XXX

Once done, the idea is to launch directly salt like "salt '*' redis.bgrewriteaof instance=instance_1" by example.

The issue identifies the Redis Salt module and minion configuration as the starting points; first inspect how the current single Redis instance is read and how redis.bgrewriteaof arguments are dispatched. Define the named-instance configuration and instance selection behavior, then add coverage showing both instances can be targeted.