Test Django 4.0 (#8280)

* Test Django 4.0

Django 4.0 released today.

* Test Django 4.0

* Test Django 4.0

* Test Django 4.0

README.md

@@ -55,7 +55,7 @@ There is a live example API for testing purposes, [available here][sandbox].
 # Requirements
 
 * Python (3.5, 3.6, 3.7, 3.8, 3.9)
-* Django (2.2, 3.0, 3.1, 3.2)
+* Django (2.2, 3.0, 3.1, 3.2, 4.0)
 
 We **highly recommend** and only officially support the latest patch release of
 each Python and Django series.

docs/index.md

@@ -86,7 +86,7 @@ continued development by **[signing up for a paid plan][funding]**.
 REST framework requires the following:
 
 * Python (3.5, 3.6, 3.7, 3.8, 3.9)
-* Django (2.2, 3.0, 3.1, 3.2)
+* Django (2.2, 3.0, 3.1, 3.2, 4.0)
 
 We **highly recommend** and only officially support the latest patch release of
 each Python and Django series.

setup.py

@@ -93,6 +93,7 @@ setup(
         'Framework :: Django :: 3.0',
         'Framework :: Django :: 3.1',
         'Framework :: Django :: 3.2',
+        'Framework :: Django :: 4.0',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: BSD License',
         'Operating System :: OS Independent',

tox.ini

@@ -24,7 +24,7 @@ deps =
         django22: Django>=2.2,<3.0
         django31: Django>=3.1,<3.2
         django32: Django>=3.2,<4.0
-        django40: Django>=4.0rc1,<5.0
+        django40: Django>=4.0,<5.0
         djangomain: https://github.com/django/django/archive/main.tar.gz
         -rrequirements/requirements-testing.txt
         -rrequirements/requirements-optionals.txt