Bugfix/do not overwrite stable at (#4304)

* Fixes race condition where the updated incident is marked as stable, but the update flow has not yet completed.

* Reduces likelihood of incident_update_flow() running before incident_service.update() completes.

* Adds a check to only set the stable at field if the incident is not active and the stable_at field has not been set yet.

* Restores previous version of incident update functions

* Do not overwrite the incident stable_at field when calculating incident costs.

* Default participant_role_renounced_at is set to utcnow

src/dispatch/incident_cost/service.py

@@ -214,22 +214,18 @@ def calculate_incident_response_cost_with_classic_model(incident: Incident, inci
                 continue
 
             participant_role_assumed_at = participant_role.assumed_at
+            # we set the renounced_at default time to the current time
+            participant_role_renounced_at = datetime.utcnow()
 
             if incident.status == IncidentStatus.active:
-                # we set the renounced_at default time to the current time
-                participant_role_renounced_at = datetime.utcnow()
-
                 if participant_role.renounced_at:
                     # the participant left the conversation or got assigned another role
                     # we use the role's renounced_at time
                     participant_role_renounced_at = participant_role.renounced_at
             else:
-                # Fixes race condition where the updated incident is marked as stable, but the update flow has not yet completed.
-                if not incident.stable_at:
-                    incident.stable_at = datetime.utcnow()
-
-                # we set the renounced_at default time to the stable_at time
-                participant_role_renounced_at = incident.stable_at
+                # we set the renounced_at default time to the stable_at time if the stable_at time exists
+                if incident.stable_at:
+                    participant_role_renounced_at = incident.stable_at
 
                 if participant_role.renounced_at:
                     # the participant left the conversation or got assigned another role