flows: optimise queries for flow and stage API endpoints

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/flows/api/flows.py

@@ -80,7 +80,7 @@ class FlowSerializer(ModelSerializer):
 class FlowViewSet(UsedByMixin, ModelViewSet):
     """Flow Viewset"""
 
-    queryset = Flow.objects.all()
+    queryset = Flow.objects.all().prefetch_related("stages")
     serializer_class = FlowSerializer
     lookup_field = "slug"
     ordering = ["slug", "name"]

authentik/flows/api/stages.py

@@ -61,7 +61,7 @@ class StageViewSet(
     filterset_fields = ["name"]
 
     def get_queryset(self):  # pragma: no cover
-        return Stage.objects.select_subclasses()
+        return Stage.objects.select_subclasses().prefetch_related("flow_set")
 
     @extend_schema(responses={200: TypeCreateSerializer(many=True)})
     @action(detail=False, pagination_class=None, filter_backends=[])