* Update linting configuration
This removes flake8 in favor of ruff, which also provides isort support, and
updates all files to be black, isort, and ruff compliant. This also adds black
and ruff checks to the tox and Github linting workflow.
* Tweak the code coverage config and calls
I'd want to advice against using `use_connection()` more, as the
connection setup is less explicit, and also pollutes global memory.
Because, well:
$ python -m this | head -n4 | tail -n1
;)