Update to make it work again

[mir06]

There were only some small changes to make the code work with radicale>=3.1.2 (see the commits with the type fix). The test data had to be adapted as well. I updated the README to reflect the changes already done in `0.0.16.

And I ran ruff check and ruff format for a consistent formatting.

[kyokenn]

And I ran ruff check and ruff format for a consistent formatting.

Please, don't do it. It makes PR huge for unnecessary changes like quotes replacement ' -> " Thanks for the PR anyway. Which CalDAV/CardDAV clients did you used for testing this?

[mir06]

Sorry for the ruff. I just reverted to the previous commit.

[mir06]

I tested with thunderbird and evolution on the desktop but not with DAVx5 on the mobile.

[mir06]

Dear @kyokenn, any chance you will have a look at the MR?

[kyokenn]

Thanks for the MR!