Adding in support for Python 3.13

[abeed-avayu]

Description

This adds support for Python 3.13. I think I've got all the references, but there's probably somewhere else that I've overlooked.

Shout-out to London Django Meetup for the Hacktoberfest Hackathon inspiration. CC @adamchainz et al.

Testing notes

I ran this under docker (python:3.13-slim) locally and make test and make coverage passed all the tests. Would have also tried with a virtualenv but pyenv didn't have 3.13 (non-RC) at the time of testing.

Checklist:

• [ x ] I have added the relevant tests for this change.
• [ x ] I have added an item to the Pending section of docs/changes.rst.

[matthiask]

Thanks! The failures are probably due to psycopg2 not having 3.13-compatible wheels yet. (psycopg/psycopg2#1729)

I added some comments.

[abeed-avayu]

I've probably overstepped the mark by removing 3.8 as it's end of life, but as the next version release looks to be a major one I thought it would be compatible with that. Let me know if that's a problem and I'll reinstate it.

[matthiask]

I've probably overstepped the mark by removing 3.8 as it's end of life, but as the next version release looks to be a major one I thought it would be compatible with that. Let me know if that's a problem and I'll reinstate it.

On a pedantic day I'd like this to happen with a separate pull request. Today I'm feeling generous :) I think supporting 5 minor Python versions at the same time is enough and I'm therefore fine with it. CI isn't free energy wise after all.

[matthiask]

You can remove 38 here and below as well.

[abeed-avayu]

So still struggling a bit to get the matrix running correctly. I think we only want py313 with dj51 and main, and then postgres and postgis DB backends but using psycopg as the adapter library.

[matthiask]

Thank you for your contribution!