Replace "black style" with ruff #589
Description
I'm not much happy with the "black style" messing up the code all the time, ruff seems to be a better and more modern solution, and it checks for more things than just the code style.
(I find it incredibly annoying that long lines are converted into an unreadable multiline spaghetti, it's particularly frustrating in cases where the code looks nice and clean with several similar-looking lines in a row, and then black style goes in and wraps one of them into some multi-line spaghetti. Or perhaps I should just try to learn to keep my lines shorter (that could involve renaming variables from long_and_descriptive_variable_name to cqz6 ... or perhaps not). It's been suggested that I relax this setting in "black style", but I've been gritting my teeth, considering that PEPs and community standards is more important than my personal taste. However, interestingly, it seems like the "current best practice" is to not set up ruff to do excessive line wrapping).
Changing from black to ruff will involve major code-style changes. It will cause a lot of pain for anyone maintaining forks of the caldav library, as well as for myself if I happen to have any outstanding work in git branches / pull requests. This change should probably be done after closing up and reviewing all outstanding pull requests but just before a release.
One idea could be to try starting with some few files, the least commonly used files. Also, ruff has lots of configuration options and opt-in/opt-out features, so it could be possible to introduce the ruff style slowly. Though, maybe it's better to "rip off the band aid" (or plunge into the cold bathing water) rather than distribute the pain over a longer time frame.