fix(aci): Return empty list from open periods endpoint when detector has no linked group

[jasonyuezhang]

This is an expected state, so IMO it should be a successful response with an empty list instead of a 404. This makes things simpler on the UI side.

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Copied from getsentry#101046
Original PR: getsentry#101046

[propel-test-bot]

Return Empty List When No Group Linked in Open Periods Endpoint

This PR updates the organization_open_periods.py API endpoint to return an empty list (HTTP 200) instead of a 404 error when there is no group linked to a detector. Corresponding test coverage in test_organization_open_periods.py is modified to expect and assert the new successful empty response rather than an error. The change aligns the API response with an expected, non-error state, thereby simplifying UI handling on the client side.

Key Changes

• In src/sentry/workflow_engine/endpoints/organization_open_periods.py, replaced Response with 404 status and error message for missing groups with a call to self.paginate on an empty queryset, returning an empty list and HTTP 200.
• Updated tests/sentry/workflow_engine/endpoints/test_organization_open_periods.py to assert empty list responses when no group is linked to a detector, removing previous checks for 404 and error detail.
• Removed unused import of status from rest_framework in both the endpoint and test files.

Affected Areas

• src/sentry/workflow_engine/endpoints/organization_open_periods.py
• tests/sentry/workflow_engine/endpoints/test_organization_open_periods.py

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