Bump django-filter from 2.4.0 to 21.1

Bumps django-filter from 2.4.0 to 21.1.

Changelog

Sourced from django-filter's changelog.

Version 21.1 (2021-9-24)

This is a maintenance release updating CI testing for the latest non-end-of-life versions of Python and Django, and updating package metadata accordingly.

With this release django-filter is switching to a two-part CalVer versioning scheme, such as 21.1. The first number is the year. The second is the release number within that year.

On an on-going basis, Django-Filter aims to support all current Django versions, the matching current Python versions, and the latest version of Django REST Framework.

Please see:

• Status of supported Python branches <https://devguide.python.org/#status-of-python-branches>_
• List of supported Django versions <https://www.djangoproject.com/download/#support-versions>_

Support for Python and Django versions will be dropped when they reach end-of-life. Support for Python versions will dropped when they reach end-of-life, even when still supported by a current version of Django.

Other breaking changes are rare. Where required, every effort will be made to apply a "Year plus two" deprecation period. For example, a change initially introduced in 23.x would offer a fallback where feasible and finally be removed in 25.1. Where fallbacks are not feasible, breaking changes without deprecation will be called out in the release notes.

Beyond that change, there are few changes. Some small bugfixes, improvements to localisation, and documentation tweaks. Thanks to all who were involved.

Commits

• 54d143f Update change notes for 21.1 release.
• e748084 Bumped version for 21.1 release.
• 16c4737 Removed explicit supported Python/Django version numbers from docs.
• edcf5f3 Update README for use of CalVer.
• 59f6431 Added Trove classifier for Django 4.0.
• 22da0e1 Added Django 4.0 to test matrix.
• afa4e43 Adjusted tests for Django 4.0.
• 5a16562 Removed remaining separate mock library usages.
• 43fd440 Fixed typo in tips.txt (#1437)
• 512310f Updated Gettext plural forms to match Django (#1392)
• Additional commits viewable in compare view

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