Fix documentation on dynamic class loading for forked dashboard apps

docs/source/releases/v2.0.rst

   ``include(application.urls[0])``, which only passes in the list of URL
   patterns.
 
+  .. note::
+
+    Because of the way dynamic class loading now works, when forking dashboard
+    apps, the ``oscar.apps.dashboard`` app also needs to be forked; and the
+    forked dashboard app's code must live inside the forked
+    ``oscar.apps.dashboard`` app's directory.
+
+    Similarly, when forking ``oscar.apps.catalogue.reviews``,
+    ``oscar.apps.catalogue`` needs to be forked as well; and the forked
+    ``oscar.apps.catalogue.reviews`` app's code must live inside the forked
+    ``oscar.apps.catalogue`` app's directory.
+
 Dependency changes
 ------------------
 

docs/source/topics/fork_app.rst

   But there's no need to do this manually anymore! More information is
   available in :ref:`fork-oscar-app`.
 
+.. note::
+
+  Because of the way dynamic class loading works, when forking dashboard apps,
+  the ``oscar.apps.dashboard`` app also needs to be forked; and the forked
+  dashboard app's code must live inside the forked ``oscar.apps.dashboard``
+  app's directory.
+
+  Similarly, when forking ``oscar.apps.catalogue.reviews``,
+  ``oscar.apps.catalogue`` needs to be forked as well; and the forked
+  ``oscar.apps.catalogue.reviews`` app's code must live inside the forked
+  ``oscar.apps.catalogue`` app's directory.
+
 Create Python module with same label
 ====================================