Fixes #18900: raise QuerySetNotOrdered exception when trying to paginate unordered API querysets (#19943)

* Fixes #18900: introduce/raise QuerySetNotOrdered exception

Defines a new exception, `QuerySetNotOrdered`, and raises it in
`OptionalLimitOffsetPagination.paginate_queryset` in the right
conditions:
- the iterable to be paginated is a QuerySet isinstance
- the `queryset.ordered` flag is not truthy

* Don't try to reapply ordering if ordering is already present

* Add ordering for failing tagged-objects list API endpoint

I chose to implement this here for TaggedItemViewSet, rather than on the
model, because any meaningful ordering is going to be done on the
related Tag instance and I didn't want to introduce potential, not well
understood side-effects by applying a model-wide ordering via a related
model field.

* Add default Token ordering behavior

* Adds basic tests for raising QuerySetNotOrdered

* Note why ordering is not applied in TaggedItem.Meta

netbox/extras/api/views.py

@@ -185,7 +185,9 @@ class TagViewSet(NetBoxModelViewSet):
 
 
 class TaggedItemViewSet(RetrieveModelMixin, ListModelMixin, BaseViewSet):
-    queryset = TaggedItem.objects.prefetch_related('content_type', 'content_object', 'tag')
+    queryset = TaggedItem.objects.prefetch_related(
+        'content_type', 'content_object', 'tag'
+    ).order_by('tag__weight', 'tag__name')
     serializer_class = serializers.TaggedItemSerializer
     filterset_class = filtersets.TaggedItemFilterSet