Django 4.2 and fix tests

[blag]

Closes #354, but also does more.

This PR is prep for a release. I'd like to get CI passing before I submit a PR to bump the version as part of a release.

Changes proposed in this PR:

• Move accounts/tests to ./tests (so we don't distribute tests with package)
• Use timezone-aware now() in middleware
• Fix tests
• Use ruff
• Drop Django 2.2, and Python 3.6 and 3.7
• Update GHA config

Tips for an ideal PR

• You have read our Code of Conduct: https://github.com/pinax/.github/blob/master/CODE_OF_CONDUCT.md
• You have read our Contributing info: https://github.com/pinax/.github/blob/master/CONTRIBUTING.md
• The PR is atomic
• Unit tests have been updated/added, if needed
• App version number has been updated in setup.py (Pinax uses SemVer)
• Change Log has been updated
• You have added your name to the AUTHORS file

[blag]

Not sure how to use GHA and turn off DeepSource. 😕

[uhurusurfa]

You would have to raise the PR from a branch within the repo to stop Deepsource running.

What is replacing the purpose that deepsource p[rovides?

[blag]

Gotcha, thanks, I'm not familiar with DeepSource. I was only removing it because I didn't recognize it, it was added 4 years ago, and I saw another PR that used GHA.

I'll close this and open another PR from within the repo.

[uhurusurfa]

GHA does not currently offer any builtin functionality that I am aware of to do code analysis.
Leave deepsource in and fix any reported isues.