Drop Django 3.2 support

Django 3.2 support was dropped. Django 3.2 ends its extended support
in April 2024[1]. Considering this, horizon dropped Django 3.2 support
and used Django 4.2 as the default version of Django. It also updates
some references to Django 4.2 from Django 3.2 in the documentation.

[1] https://www.djangoproject.com/download/

Change-Id: I9fff310c5433cf96cdf0a2cd81d11a96c2a4a55b

doc/source/contributor/testing.rst

@@ -107,15 +107,15 @@ when a test fails you can use::
 
   $ tox -e py37 -- --pdb
 
-py3-dj32
+py3-dj42
 -----------------------------
 
-Runs the Python unit tests against Django 3.2.
+Runs the Python unit tests against Django 4.2.
 
-py36
-----
+py311
+-----
 
-Runs the Python unit tests with a Python 3.6 environment.
+Runs the Python unit tests with a Python 3.11 environment.
 
 releasenotes
 ------------

doc/source/install/system-requirements.rst

@@ -2,11 +2,11 @@
 System Requirements
 ===================
 
-The Ussuri release of horizon has the following dependencies.
+The Caracal release of horizon has the following dependencies.
 
-* Python 3.6 or 3.7
+* Python 3.8 or 3.11
 
-* Django 3.2
+* Django 4.2
 
   * Django support policy is documented at :ref:`django_support`.
 

releasenotes/notes/drop-django3.2-support-94b52cf6d175a818.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Django 3.2 support was dropped. Django 3.2 ends its extended support
+    in April 2024. Considering this horizon dropped Django 3.2 support
+    and uses Django 4.2 as default.

requirements.txt

@@ -16,7 +16,7 @@ pbr>=5.5.0 # Apache-2.0
 # Horizon Core Requirements
 Babel>=2.6.0 # BSD
 debtcollector>=1.2.0 # Apache-2.0
-Django>=3.2,<4.3 # BSD
+Django>=4.2,<4.3 # BSD
 django-compressor>=2.4.1 # MIT
 django-debreach>=1.4.2 # BSD License (2 clause)
 django-pyscss>=2.0.2 # BSD License (2 clause)