[Feature Request]: External Alertmanager Contact Point and Notification Policy Support

[asreich]

Feature Request

Thanks to the newly added AlertRuleGroup,AlertContactPoint,AlertNotificationPolicy targets we can pull these new resources but not from configurations that use an External Alertmanager to handle Grafana Cloud Alert Rules. The AlertRuleGroups can be synced easily enough but all of the Contact points and Notification Policies I have setup in the external Alertmanager cannot be.

My use case is migrating from on-prem Grafana OSS to Grafana Cloud and Grizzly is making it super easy. I can manually create these Contact Points and Notification Policies to make things work but just wanted to highlight a gap that would be hugely helpful for other people's migration prospects.

Thanks for your work on this project!

[Itaykal]

Mimir uses alertmanager configuration per tenant (as far as I know of) instead of the abstraction of notification policies and contact points, I think the best way to handle it is to expose external alertmanager configuration instead of the abstractions themselves.