Fixed #27910 -- Added enumeration helpers for use in Field.choices.

These classes can serve as a base class for user enums, supporting
translatable human-readable names, or names automatically inferred
from the enum member name.

Additional properties make it easy to access the list of names, values
and display labels.

Thanks to the following for ideas and reviews:

Carlton Gibson, Fran Hrženjak, Ian Foote, Mariusz Felisiak, Shai Berger.

Co-authored-by: Shai Berger <shai@platonix.com>
Co-authored-by: Nick Pope <nick.pope@flightdataservices.com>
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

docs/topics/db/models.txt

@@ -198,6 +198,19 @@ ones:
         >>> p.get_shirt_size_display()
         'Large'
 
+    You can also use enumeration classes to define ``choices`` in a concise
+    way::
+
+        from django.db import models
+
+        class Runner(models.Model):
+            MedalType = models.TextChoices('MedalType', 'GOLD SILVER BRONZE')
+            name = models.CharField(max_length=60)
+            medal = models.CharField(blank=True, choices=MedalType.choices, max_length=10)
+
+    Further examples are available in the :ref:`model field reference
+    <field-choices>`.
+
 :attr:`~Field.default`
     The default value for the field. This can be a value or a callable
     object. If callable it will be called every time a new object is