Python3-saml-django

- Update to Python 3.11
- Update to Django 4.2
- Drop support for Django 2.x

- Add `SAML_ATTR_DEFAULTS` setting that allows missing attributes to be set to a default value
- Create `MissingAttributeException` that will clearly indicate missing attributes
- Correct User backend to authenticate in an atomic transaction to prevent unexpected behavior with new users logging in for the second time if `reconfigure_user` throws an exception

What's Changed
* Correct IdP URL Caching & `server_port` key in request data by ngearhart in https://github.com/penn-state-dance-marathon/python3-saml-django/pull/19
* Add Setting to Ignore Some Fields When Updating a User Instead of Creating by ngearhart in https://github.com/penn-state-dance-marathon/python3-saml-django/pull/20


**Full Changelog**: https://github.com/penn-state-dance-marathon/python3-saml-django/compare/v1.2.0...v1.2.1

Add Django 4.0 and Python 3.10 support, remove Django 1.11 and Python 3.6 support.

Thanks to quique - Properly handle a SingleLogout initiated by other SP 9

Add support for Django 3.0, 3.1, and 3.2, and Python 3.9. Drop support for Python 3.5.