Refs #27272 -- Added Collector.add_dependency().

django/db/models/deletion.py

@@ -102,11 +102,15 @@ class Collector:
         # deleting, and therefore do not affect the order in which objects have
         # to be deleted.
         if source is not None and not nullable:
-            if reverse_dependency:
-                source, model = model, source
-            self.dependencies[source._meta.concrete_model].add(model._meta.concrete_model)
+            self.add_dependency(source, model, reverse_dependency=reverse_dependency)
         return new_objs
 
+    def add_dependency(self, model, dependency, reverse_dependency=False):
+        if reverse_dependency:
+            model, dependency = dependency, model
+        self.dependencies[model._meta.concrete_model].add(dependency._meta.concrete_model)
+        self.data.setdefault(dependency, self.data.default_factory())
+
     def add_field_update(self, field, value, objs):
         """
         Schedule a field update. 'objs' must be a homogeneous iterable