Update ci and code

[sevdog]

This PR performs some updates:

• Update CI to work on github actions rather than travis.ci
• Add django 5.0 and python 3.11/3.12, remove python 3.7 from CI
• Update codebase to better use python 3.8 features
• Remove raw SQL formatting in tests (which is a bad practice)
• Refactor encryption to reduce code redundancy in JSONField
• Refactor validators definition for IntegerField to avoid copypasting code from django and to address connection specific limits

[artursmet]

Hi,

Looks like we have introduced almost the same changes regarding the CI setup 😅 #19 Since your changeset covers a lot more, I'm happy to close my PR and wait for your changes to be merged.

[frgmt]

@sevdog @artursmet Thank you both!

[sevdog]

Seems that I forgot to explicity setup the codecov token for upload, the solution would be to add the that step (as pointed here)

      env:
        CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

Which is the name of the secret in which codecov token is stored?

[frgmt]

@sevdog I'm not code owner now and I can't change settings. So I don't really know if I can set up token.. 🙏
Should we ask the jazzband maintainers?