fix(django): Keep Django 2.2 support for upgrade purposes

[AniketDas-Tekky]

Dropping Django 2.2 support while adding Django 3.2 support make it very difficult for people trying to upgrade from 2.2 to 3.2.

[charettes]

Could you elaborate on how the recent changes make it very difficult for people trying to upgrade from 2.2 to 3.2?

It's only metadata changes, what prevents you from running django-picklefields=3.0.1 against 3.2?

#61 has proven that no application level changes are required to update from one to the other (django-picklefields=3.0.1 works with Django 3.2). I'm aware of any Python package managers that enforces dependencies of Pypi classifiers so I'm struggling to understand the origin of the difficulty you are referring to.

[AniketDas-Tekky]

@charettes I see what you mean by no application level changes. I was only looking at "supported versions" and not at the actual changes.

The difficulty I was referring to was that I need to update my dependencies before updating django , all without breaking compatibility throughout the process. I would like to use 3.1.0 so that our dependencies are up to date, but I can't update it without seeing CI pass for django 2.2

[AniketDas-Tekky]

We could run our own CI against Django 2.2 to get some assurance, but that will fail unless we at least relax the install_requires here, right?

[adamchainz]

This issue is nearly two years old, let’s close it now?

[charettes]

yep, no point in keeping that one opened anymore.