Django package

[d-flood]

This PR removes the URL namespace so that this update no longer includes breaking changes for upstream users.

Additional items mentioned by @ColeDCrawford below:

• Test matrix should cover Python 3.9 - 3.13
• Pin PSQL to v15 or v16 in docker-compose config files
• Remove version key in docker-compose config files
• Switch to python3.12 in Dockerfile
• [ ] See whether we can pin Django to 5.x series?
• Bump version to 3.0.0 and document any process for building Github releases

[ColeDCrawford]

Other items. These don't need to be addressed in this PR, but should be in the artshumrc:django-5 -> nmaekawa:master PR

• Test matrix should cover Python 3.9 - 3.13
• Pin PSQL to v15 or v16 in docker-compose config files
• Remove version key in docker-compose config files
• Switch to python3.12 in Dockerfile
• See whether we can pin Django to 5.x series?
• Bump version to 3.0.0 and document any process for building Github releases

[d-flood]

• See whether we can pin Django to 5.x series?

I got to all but this one. If the current Django versions is >=4.2, then it seems like the upstream probably wants to stick with long support to long support? Since 5.2 isn't released yet, I'd lean toward leaving it at >=4.2, which doesn't prevent us from using latest 5.1x.

[ColeDCrawford]

Think this is all set now. Just pushed a few small changes to finish deprecating Python 3.8 and updating the package metadata.