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  django-jsonfield makes use of that import, and is no longer being
  updated.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/requirements.in

@@ -9,14 +9,14 @@ cryptography>=3.2
 Cython<3 # Since the bump to PyYAML 5.4.1 this is now a mandatory dep
 daphne
 distro
-django==2.2.24  # see UPGRADE BLOCKERs
+django==3.0.14  # see UPGRADE BLOCKERs
 django-auth-ldap
 django-cors-headers>=3.5.0
 django-crum
 django-extensions>=2.2.9  # https://github.com/ansible/awx/pull/6441
-django-guid==2.2.0  # pinned to match Django 2.2
-django-jsonfield==1.2.0  # see UPGRADE BLOCKERs
-django-oauth-toolkit==1.1.3  # see UPGRADE BLOCKERs
+django-guid==2.2.1  # see https://pypi.org/project/django-guid/ for supported versions
+django-jsonfield==1.4.1
+django-oauth-toolkit==1.4.1
 django-polymorphic
 django-pglocks
 django-qsstats-magic
@@ -40,7 +40,7 @@ psycopg2
 psutil
 pygerduty
 pyparsing
-python3-saml
+python3-saml==1.13.0
 python-dsv-sdk
 python-tss-sdk==1.0.0
 python-ldap>=3.3.1 # https://github.com/python-ldap/python-ldap/issues/270