Removes EOL Python version support and adjusts the test matrix to account

[stumpylog]

This PR removes support for very End Of Life Python versions. Namely this is Python 2.7 support, as well as 3.5 through 3.7.

It also adjusts the supported/tested Django versions to only include either LTS or those listed here in Django's documentation.

[friedelwolff]

Thank you for your contribution, and sorry that I only get round to looking at it now. Unfortunately I just merged PR #16 before looking at this, and I see you covered a lot of similar ground. However, you cover a few more cleanups that would be good. It would be kind if you can rebase your changes on top of master and resubmit. Thank you!

[stumpylog]

I believe this is up to date now, based on the latest Django versions: https://docs.djangoproject.com/en/5.1/faq/install/#faq-python-version-support

It includes testing with 5.1 as well, as just released a bit ago, so you may want to mention that in release notes.

[stumpylog]

Also, if you would like (separate from this PR), we could modernize the packaging now, such as using hatch with a pyproject.toml file. It can handle building distributions, testing, linting and with matrices, replace tox.

[stumpylog]

@friedelwolff Let me know if there's additional things for this pull request

[bartvanandel]

I suppose before merging this one, Python 3.13 can be added, and Python 3.8 can be removed?

[bartvanandel]

Probably a good idea to remove for other EOL versions of Django too:

• Django 3.2: EOL since 01 April 2024
• Django 4.1: EOL since 01 April 2023
• Django 5.0: EOL since 02 April 2025

And to add Django 5.2 to the matrix, which was released on 02 April 2025.

[stumpylog]

Before I bother with doing that work, it'd be nice to see if this project is alive

[stumpylog]

@friedelwolff I'd be happy to help do some maintenance for this library if you're interested in help.