[3.0.x] Fixed #31124 -- Fixed setting of get_FOO_display() when overriding inherited choices.

Regression in 2d38eb0ab9

Backport of 29c126bb34 from master

docs/ref/models/instances.txt

@@ -829,6 +829,15 @@ Note that in the case of identical date values, these methods will use the
 primary key as a tie-breaker. This guarantees that no records are skipped or
 duplicated. That also means you cannot use those methods on unsaved objects.
 
+.. admonition:: Overriding extra instance methods
+
+    In most cases overriding or inheriting ``get_FOO_display()``,
+    ``get_next_by_FOO()``, and ``get_previous_by_FOO()` should work as
+    expected. Since they are added by the metaclass however, it is not
+    practical to account for all possible inheritance structures. In more
+    complex cases you should override ``Field.contribute_to_class()`` to set
+    the methods you need.
+
 Other attributes
 ================
 

docs/releases/3.0.3.txt

@@ -31,3 +31,7 @@ Bugfixes
   :class:`~django.contrib.postgres.aggregates.ArrayAgg` and
   :class:`~django.contrib.postgres.aggregates.StringAgg` with ``filter``
   argument when used in a ``Subquery`` (:ticket:`31097`).
+
+* Fixed a regression in Django 2.2.7 that caused
+  :meth:`~django.db.models.Model.get_FOO_display` to work incorrectly when
+  overriding inherited choices (:ticket:`31124`).