Upgrade to Django 3.0

- upgrades
  - Django 3.0.14
  - django-jsonfield 1.4.1 (from 1.2.0)
  - django-oauth-toolkit 1.4.1 (from 1.1.3)
    - Stopping here because later versions have changes to the
      underlying model to support OpenID Connect.  Presumably this can
      be dealt with via a migration in our project.
  - django-guid 2.2.1 (from 2.2.0)
  - django-debug-toolbar 3.2.4 (from 1.11.1)
  - python3-saml 1.13.0 (from 1.9.0)
  - xmlsec 1.3.12 (from 1.3.3)

- Remove our project's use of django.utils.six in favor of directly
  using six, in awx.sso.fields.

- Temporarily monkey patch six back in as django.utils.six, since
  django-jsonfield makes use of that import, and is no longer being
  updated.  Hopefully we can do away with this dependency with the new
  generalized JSONField brought in with Django 3.1.

- Force a json decoder to be used with all instances of JSONField
  brought in by django-jsonfield.  This deals with the 'cast to text'
  problem noted previously in our UPGRADE_BLOCKERS.

- Remove the validate_uris validator from the OAuth2Application in
  migration 0025, per the UPGRADE_BLOCKERS, and remove that note.

- Update the TEMPLATES setting to satisfy Django Debug Toolbar.  It
  requires at least one entry that has APP_DIRS=True, and as near as I
  can tell our custom OPTIONS.loaders setting was effectively doing
  the same thing as Django's own machinery if this setting is set.

requirements/README.md

@@ -58,7 +58,7 @@ Make sure to delete the old tarball if it is an upgrade.
 Anything pinned in `*.in` files involves additional manual work in
 order to upgrade. Some information related to that work is outlined here.
 
-### django
+### Django
 
 For any upgrade of Django, it must be confirmed that
 we don't regress on FIPS support before merging.
@@ -90,13 +90,10 @@ that we have the latest version
 
 ### django-oauth-toolkit
 
-Version 1.2.0 of this project has a bug that error when revoking tokens.
-This is fixed in the master branch but is not yet released.
-
-When upgrading past 1.2.0 in the future, the `0025` migration needs to be
-edited, just like the old migration was edited in the project:
-https://github.com/jazzband/django-oauth-toolkit/commit/96538876d0d7ea0319ba5286f9bde842a906e1c5
-The field can simply have the validator method `validate_uris` removed.
+Versions later than 1.4.1 throw an error about id_token_id, due to the
+OpenID Connect work that was done in
+https://github.com/jazzband/django-oauth-toolkit/pull/915.  This may
+be fixable by creating a migration on our end?
 
 ### azure-keyvault
 
@@ -117,7 +114,7 @@ https://github.com/adamchainz/django-jsonfield/pull/14
 
 This breaks a very large amount of AWX code that assumes these fields
 are returned as dicts. Upgrading this library will require a refactor
-to accomidate this change.
+to accommodate this change.
 
 ### pip and setuptools