fix alert group page bug (#5105)

# What this PR does

fixes a bug where it's not possible to view an alert group older than 30
days

<img width="623" alt="Screenshot 2024-10-01 at 14 36 00"
src="https://github.com/user-attachments/assets/c06c923e-4c1c-4873-bf4b-9296cfbbb312">

## Which issue(s) this PR closes

the bug was introduced in https://github.com/grafana/oncall/pull/5067

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## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

engine/apps/api/tests/test_alert_group.py

@@ -2344,3 +2344,41 @@ def test_alert_group_external_urls(
         "url": "https://some-url",
     }
     assert response.json()["external_urls"] == [expected]
+
+
+@pytest.mark.django_db
+def test_filter_default_started_at(
+    make_organization_and_user_with_plugin_token,
+    make_alert_receive_channel,
+    make_channel_filter,
+    make_alert_group,
+    make_alert,
+    make_user_auth_headers,
+):
+    organization, user, token = make_organization_and_user_with_plugin_token()
+    alert_receive_channel = make_alert_receive_channel(organization)
+    channel_filter = make_channel_filter(alert_receive_channel, is_default=True)
+
+    old_alert_group = make_alert_group(alert_receive_channel, channel_filter=channel_filter)
+    old_alert_group.started_at = timezone.now() - timezone.timedelta(days=31)
+    old_alert_group.save(update_fields=["started_at"])
+    make_alert(alert_group=old_alert_group, raw_request_data=alert_raw_request_data)
+
+    new_alert_group = make_alert_group(alert_receive_channel, channel_filter=channel_filter)
+    make_alert(alert_group=new_alert_group, raw_request_data=alert_raw_request_data)
+
+    client = APIClient()
+
+    # by default, no alert groups older than 30 days should be listed
+    response = client.get(reverse("api-internal:alertgroup-list"), **make_user_auth_headers(user, token))
+    assert response.status_code == status.HTTP_200_OK
+    assert len(response.json()["results"]) == 1
+    assert response.json()["results"][0]["pk"] == new_alert_group.public_primary_key
+
+    # but it should still be possible to retrieve an old alert group by its ID
+    response = client.get(
+        reverse("api-internal:alertgroup-detail", kwargs={"pk": old_alert_group.public_primary_key}),
+        **make_user_auth_headers(user, token),
+    )
+    assert response.status_code == status.HTTP_200_OK
+    assert response.json()["pk"] == old_alert_group.public_primary_key

engine/apps/api/views/alert_group.py

@@ -332,8 +332,7 @@ class AlertGroupView(
         alert_receive_channels_ids = list(alert_receive_channels_qs.values_list("id", flat=True))
         queryset = AlertGroup.objects.filter(channel__in=alert_receive_channels_ids)
 
-        # This is a quick fix to speed up requests from mobile app by adding default `started_at` filter value
-        if not self.request.query_params.get("started_at"):
+        if self.action in ("list", "stats") and not self.request.query_params.get("started_at"):
             queryset = queryset.filter(started_at__gte=timezone.now() - timezone.timedelta(days=30))
 
         if self.action in ("list", "stats") and settings.ALERT_GROUPS_DISABLE_PREFER_ORDERING_INDEX: