Currently it’s possible to create ‘assignment_notification_rule’ via API: https://api-reference.pagerduty.com/#!/Users/post_users_id_notification_rules but it does not seem to be possible to create a a notification rule that would be triggered on high-urgency event change.
This would be a great help for users (like me) that manage pagerduty resources via IaaC solutions (Terraform in my case).
API: implement creation of change_notification_rule
The assignment_notification_rule in the notification rules REST API endpoint corresponds with the status update notification rules in the web UI. This feature allows you to configure notification rules when an incident assigned to you changes status (i.e. is acknowledged, resolved, or escalated).
If an incident is changed from low to high urgency, it will immediately kick off the high urgency notification rules for the users assigned to that incident. So if one of your incidents is updated to high urgency, you would be notified for these incidents as a responder, following your high urgency notification rules.