Is your feature request related to a problem? Please describe:
Not a problem, however it would be nice if we could allow go-alert to manage the users in our support slack group, that way we could automatically match go-alert's on call rotation with who is assigned to the slack group.

Describe the solution you'd like:
When a go-alert rotation ends:

• go alert would add the new on-call users (primary and secondary rotations) to a configured slack group
• go alert would remove the old on-call users (primary and secordary rotations) from the same configured slack group

Describe alternatives you've considered:
Currently our team does this manually, however because our goalert rotation ends at midnight thursday evening. Because of this we tend to either update the slack group with the new on call rotation either the day before the rotation ends, or the morning after, potentially sending some of our slack based notifications to the wrong on call group (i.e. if someone asks for help from our @<team-name>-support group in slack.

Additional context:
N/A

Thanks so much!