modernization of code base - better support for newer python releases

[skewty]

Would the PAHO team be willing to drop support for end-of-life python releases and maybe move towards a more modern code-base with type hints?

Perhaps a v2.0 milestone?

https://devguide.python.org/versions/

Such an effort would likely go quickly. I am thinking something along the lines of >= v3.9 but perhaps even greater depending on how ambitious the effort becomes.

Proper asyncio code support is also long overdue.

Projects such as https://github.com/sbtinstruments/aiomqtt would likely be on-board to help out as well as myself.

[PierreF]

Recent PRs & commit modernized code base. We dropped support for Python < 3.7.

Asyncio is unchanged, and will probably be out-of-scope for next release.

Some changes includes:

• Update build (Modernize build (to Hatch) #774)
• Update tests and linters (Replace flake8 + isort + bandit with ruff #770 CI: Test on newer Pythons; enable Python dev mode #771 Add pre-commit plus a GItHub Action to run it #776 Convert homespun tests to conventional tests #780)
• Better typing (Add typing with mypy #791)

With exception to asyncio, do you see other modernization that should be made ?