chore(aci milestone 3): open period -> incident serializer

[jasonyuezhang]

Previously, this serializer took in an open period, fetched the incident via the IGOP lookup table, and serialized the incident. With the incident no longer guaranteed to exist, create a serializer that will populate an incident response using only the open period model.

---

Copied from getsentry#103131
Original PR: getsentry#103131

[propel-test-bot]

Replace Incident-dependent incident serializer with GroupOpenPeriod-based implementation

Adds a new implementation of WorkflowEngineIncidentSerializer and its detailed variant that produces an incident-shaped response directly from GroupOpenPeriod records. The previous flow looked up an Incident through IncidentGroupOpenPeriod (IGOP); that dependency has been removed so the API can continue working even when no matching Incident exists. Tests are rewritten accordingly.

Key Changes

• Major rewrite of src/sentry/incidents/endpoints/serializers/workflow_engine_incident.py (~+132 −95):
• • Removes broad ORM chain via WorkflowActionGroupStatus, DataCondition* etc.; now derives detectors via DetectorGroup relationship.
• • Introduces get_incident_status, get_attrs, and a simplified get_open_periods_to_detectors using fewer queries.
• • Builds fake IDs with get_fake_id_from_object_id when no Incident is found.
• • Supports optional activities expansion using GroupOpenPeriodActivity.
• • Adds WorkflowEngineDetailedIncidentSerializer that injects discoverQuery and constructs full response without Incident model.
• Updates unit tests in tests/sentry/incidents/serializers/test_workflow_engine_incident.py to assert against the new payload shape and to set up DetectorGroup fixtures.
• Removes unused imports and legacy serializers (IncidentSerializer, DetailedAlertRuleSerializer, etc.).

Affected Areas

• src/sentry/incidents/endpoints/serializers/workflow_engine_incident.py
• tests/sentry/incidents/serializers/test_workflow_engine_incident.py

This summary was automatically generated by @propel-code-bot

[propel-test-bot]

[CriticalError]

Potential KeyError when priority is not in mapping: The get_incident_status method will raise a KeyError if priority is not HIGH or MEDIUM (e.g., LOW priority). This could cause runtime failures.

Suggested Change

Suggested change

	def get_incident_status(self, priority: int | None, date_ended: datetime | None) -> int:
	if priority is None:
	raise ValueError("Priority is required to get an incident status")
	if date_ended:
	return IncidentStatus.CLOSED.value
	return self.priority_to_incident_status[priority]
	def get_incident_status(self, priority: int | None, date_ended: datetime | None) -> int:
	if priority is None:
	raise ValueError("Priority is required to get an incident status")
	if date_ended:
	return IncidentStatus.CLOSED.value
	return self.priority_to_incident_status.get(priority, IncidentStatus.WARNING.value)

⚡ Committable suggestion

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

Context for Agents

[**CriticalError**]

Potential KeyError when priority is not in mapping: The `get_incident_status` method will raise a `KeyError` if `priority` is not `HIGH` or `MEDIUM` (e.g., `LOW` priority). This could cause runtime failures.

<details>
<summary>Suggested Change</summary>

```suggestion
    def get_incident_status(self, priority: int | None, date_ended: datetime | None) -> int:
        if priority is None:
            raise ValueError("Priority is required to get an incident status")

        if date_ended:
            return IncidentStatus.CLOSED.value

        return self.priority_to_incident_status.get(priority, IncidentStatus.WARNING.value)
```

⚡ **Committable suggestion**

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

</details>

File: src/sentry/incidents/endpoints/serializers/workflow_engine_incident.py
Line: 50

[propel-test-bot]

[CriticalError]

Potential KeyError when accessing missing group detector: Line 129 accesses groups_to_detectors[group] but if a group doesn't have a corresponding detector in the detector_groups queryset, this will raise a KeyError.

Suggested Change

Suggested change

	open_periods_to_detectors = {}
	for group in group_to_open_periods:
	for op in group_to_open_periods[group]:
	open_periods_to_detectors[op] = groups_to_detectors[group]
	open_periods_to_detectors = {}
	for group in group_to_open_periods:
	detector = groups_to_detectors.get(group)
	if detector: # Only process groups that have detectors
	for op in group_to_open_periods[group]:
	open_periods_to_detectors[op] = detector

⚡ Committable suggestion

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

Context for Agents

[**CriticalError**]

Potential KeyError when accessing missing group detector: Line 129 accesses `groups_to_detectors[group]` but if a group doesn't have a corresponding detector in the `detector_groups` queryset, this will raise a `KeyError`.

<details>
<summary>Suggested Change</summary>

```suggestion
        open_periods_to_detectors = {}
        for group in group_to_open_periods:
            detector = groups_to_detectors.get(group)
            if detector:  # Only process groups that have detectors
                for op in group_to_open_periods[group]:
                    open_periods_to_detectors[op] = detector
```

⚡ **Committable suggestion**

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

</details>

File: src/sentry/incidents/endpoints/serializers/workflow_engine_incident.py
Line: 129