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

netbox/netbox/api/exceptions.py

@@ -12,3 +12,7 @@ class SerializerNotFound(Exception):
 
 class GraphQLTypeNotFound(Exception):
     pass
+
+
+class QuerySetNotOrdered(Exception):
+    pass

netbox/netbox/api/pagination.py

@@ -1,6 +1,7 @@
 from django.db.models import QuerySet
 from rest_framework.pagination import LimitOffsetPagination
 
+from netbox.api.exceptions import QuerySetNotOrdered
 from netbox.config import get_config
 
 
@@ -15,6 +16,12 @@ class OptionalLimitOffsetPagination(LimitOffsetPagination):
 
     def paginate_queryset(self, queryset, request, view=None):
 
+        if isinstance(queryset, QuerySet) and not queryset.ordered:
+            raise QuerySetNotOrdered(
+                "Paginating over an unordered queryset is unreliable. Ensure that a minimal "
+                "ordering has been applied to the queryset for this API endpoint."
+            )
+
         if isinstance(queryset, QuerySet):
             self.count = self.get_queryset_count(queryset)
         else: