[REQUEST] add `user_group_ids` to `aws_elasticache_replication_group`

[jserpapinto]

Hey guys,

Is it possible to add a user_group_ids to the aws_elasticache_replication_group?

I can make the pull request if needed, just trying to check if is something you think is ok to add.

[theprashantyadav]

Hello @jserpapinto
Added argument of user_group_ids see in PR #65