Upgrade to Django 3.2

- upgrades
  - Django 3.2.12
  - pytz 2021.3 (from 2019.3)
  - oauthlib 3.2.0 (from 3.1.0)
  - requests-oauthlib 1.3.1 (from 1.3.0)
  - django-guid 3.2.1 (from 2.2.1)
  - django-solo 2.0.0 (from 1.1.3)
  - django-taggit 2.1.0 (from 1.2.0)
  - netaddr 0.8.0 (from 0.7.19)
  - pyrad 2.4 (from 2.3)
  - django-radius devel (from 1.3.3)
  - future devel (from 0.16.0)

- django-guid, django-solo, and django-taggit are upgraded to fix the
  AppConfig deprecation warning.  FIXME: django-guid devel has the
  fix, but it hasn't been released yet.

- Released versions of django-radius have a hard-coded pin to
  future==0.16.0, which has a Python warning due to an improperly
  escaped character.  This is fixed in future devel, so for now we are
  pinning to references to the git repos.

- netaddr had a bunch of Python syntax and deprecation warnings

docs/licenses/python-future.txt

@@ -0,0 +1,19 @@
+Copyright (c) 2013-2016 Python Charmers Pty Ltd, Australia
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.