Adopting `pre-commit` and Auto Formatting

[blink1073]

We are adopting auto-formatting, including black and isort on all files. cf #889

From the Django Enhancement Proposal to use Black:

Reformatting will also be disruptive for open pull requests. One way to update them is to run Black on modified files, keep a copy aside, start a new branch from "main", move the modified files back into place, and commit the result.

Contributors will be asked to install pre-commit locally. We also have the option to use @meeseeksdev please run pre-commit on PRs if needed.