Add labels to alert group API responses (#3292)

# What this PR does

Adds a field to the internal API alert group serializer to display
labels.

## Which issue(s) this PR fixes

Related to https://github.com/grafana/oncall-private/issues/2179

## 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] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

engine/apps/api/serializers/alert_group.py

@@ -56,6 +56,19 @@ class AlertGroupFieldsCacheSerializerMixin(AlertsFieldCacheBusterMixin):
         return field
 
 
+class AlertGroupLabelSerializer(serializers.Serializer):
+    class KeySerializer(serializers.Serializer):
+        id = serializers.CharField(source="key_name")
+        name = serializers.CharField(source="key_name")
+
+    class ValueSerializer(serializers.Serializer):
+        id = serializers.CharField(source="value_name")
+        name = serializers.CharField(source="value_name")
+
+    key = KeySerializer(source="*")
+    value = ValueSerializer(source="*")
+
+
 class ShortAlertGroupSerializer(AlertGroupFieldsCacheSerializerMixin, serializers.ModelSerializer):
     pk = serializers.CharField(read_only=True, source="public_primary_key")
     alert_receive_channel = FastAlertReceiveChannelSerializer(source="channel")
@@ -105,6 +118,8 @@ class AlertGroupListSerializer(EagerLoadingMixin, AlertGroupFieldsCacheSerialize
     render_for_web = serializers.SerializerMethodField()
     render_for_classic_markdown = serializers.SerializerMethodField()
 
+    labels = AlertGroupLabelSerializer(many=True, read_only=True)
+
     PREFETCH_RELATED = [
         "dependent_alert_groups",
         "log_records__author",
@@ -150,6 +165,7 @@ class AlertGroupListSerializer(EagerLoadingMixin, AlertGroupFieldsCacheSerialize
             "declare_incident_link",
             "team",
             "grafana_incident_id",
+            "labels",
         ]
 
     @extend_schema_field(

engine/apps/api/tests/test_alert_group.py

@@ -2121,3 +2121,24 @@ def test_delete(mock_delete_alert_group, make_user_auth_headers, alert_group_int
     url = reverse("api-internal:alertgroup-detail", kwargs={"pk": "potato"})
     response = client.delete(url, **auth_headers)
     assert response.status_code == status.HTTP_404_NOT_FOUND
+
+
+@pytest.mark.django_db
+def test_alert_group_list_labels(
+    alert_group_internal_api_setup,
+    make_alert_group_label_association,
+    make_alert_receive_channel,
+    make_alert_group,
+    make_user_auth_headers,
+):
+    user, token, alert_groups = alert_group_internal_api_setup
+    make_alert_group_label_association(user.organization, alert_groups[0], key_name="a", value_name="b")
+
+    client = APIClient()
+    url = reverse("api-internal:alertgroup-list")
+    response = client.get(url, **make_user_auth_headers(user, token))
+
+    assert response.status_code == status.HTTP_200_OK
+    assert response.json()["results"][-1]["labels"] == [
+        {"key": {"id": "a", "name": "a"}, "value": {"id": "b", "name": "b"}}
+    ]