[django-filter] add support for callable queryset getter

[sevdog]

As referenced in docs:

The QuerySet argument also supports callable behavior. If a callable is passed, it will be invoked with FilterSet.request as its only argument. This allows you to easily filter by properties on the request object without having to override the FilterSet.__init__.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉