* Add notification settings to storage\domain and API models. Settings are a slice to workaround XORM mapping
* Support validation of notification settings when rules are updated
* Implement route generator for Alertmanager configuration. That fetches all notification settings.
* Update multi-tenant Alertmanager to run the generator before applying the configuration.
* Add notification settings labels to state calculation
* update the Multi-tenant Alertmanager to provide validation for notification settings
* update GET API so only admins can see auto-gen