Fixed #31007 -- Allowed specifying type of auto-created primary keys.

This also changes the default type of auto-created primary keys
for new apps and projects to BigAutoField.

docs/ref/applications.txt

@@ -90,6 +90,7 @@ would provide a proper name for the admin::
     from django.apps import AppConfig
 
     class RockNRollConfig(AppConfig):
+        default_auto_field = 'django.db.models.BigAutoField'
         name = 'rock_n_roll'
         verbose_name = "Rock ’n’ roll"
 
@@ -219,6 +220,16 @@ Configurable attributes
 
     By default, this attribute isn't set.
 
+.. attribute:: AppConfig.default_auto_field
+
+    .. versionadded:: 3.2
+
+    The implicit primary key type to add to models within this app. You can
+    use this to keep :class:`~django.db.models.AutoField` as the primary key
+    type for third party applications.
+
+    By default, this is the value of :setting:`DEFAULT_AUTO_FIELD`.
+
 Read-only attributes
 --------------------
 

docs/ref/checks.txt

@@ -378,6 +378,8 @@ Models
 * **models.W040**: ``<database>`` does not support indexes with non-key
   columns.
 * **models.E041**: ``constraints`` refers to the joined field ``<field name>``.
+* **models.W042**: Auto-created primary key used when not defining a primary
+  key type, by default ``django.db.models.AutoField``.
 
 Security
 --------

docs/ref/models/fields.txt

@@ -415,9 +415,12 @@ cross-site scripting attack.
 If ``True``, this field is the primary key for the model.
 
 If you don't specify ``primary_key=True`` for any field in your model, Django
-will automatically add an :class:`AutoField` to hold the primary key, so you
-don't need to set ``primary_key=True`` on any of your fields unless you want to
-override the default primary-key behavior. For more, see
+will automatically add a field to hold the primary key, so you don't need to
+set ``primary_key=True`` on any of your fields unless you want to override the
+default primary-key behavior. The type of auto-created primary key fields can
+be specified per app in :attr:`AppConfig.default_auto_field
+<django.apps.AppConfig.default_auto_field>` or globally in the
+:setting:`DEFAULT_AUTO_FIELD` setting. For more, see
 :ref:`automatic-primary-key-fields`.
 
 ``primary_key=True`` implies :attr:`null=False <Field.null>` and
@@ -428,6 +431,11 @@ The primary key field is read-only. If you change the value of the primary
 key on an existing object and then save it, a new object will be created
 alongside the old one.
 
+.. versionchanged:: 3.2
+
+    In older versions, auto-created primary key fields were always
+    :class:`AutoField`\s.
+
 ``unique``
 ----------
 

docs/ref/settings.txt

@@ -1245,6 +1245,17 @@ format has higher precedence and will be applied instead.
 See also :setting:`NUMBER_GROUPING`, :setting:`THOUSAND_SEPARATOR` and
 :setting:`USE_THOUSAND_SEPARATOR`.
 
+.. setting:: DEFAULT_AUTO_FIELD
+
+``DEFAULT_AUTO_FIELD``
+----------------------
+
+.. versionadded:: 3.2
+
+Default: ``'``:class:`django.db.models.AutoField`\ ``'``
+
+Default primary key field type to use for models that don't have a field with
+:attr:`primary_key=True <django.db.models.Field.primary_key>`.
 
 .. setting:: DEFAULT_CHARSET