Adding auto-formatting of code with black.

[robotrapta]

Runs server-side (github action).

[michael-groundlight]

We probably want to use this in all of our python repos, so we should consider creating a custom github action that we can just import: https://docs.github.com/en/actions/creating-actions/about-custom-actions. No need to block on this, but it's worth setting up sometime in the future.

[michael-groundlight]

In our Makefile, there is a generate target for generating the generated/ code folder from an OpenAPI spec. Let's add black to that target, as it will make the code diffs simpler (versus seeing a big diff, and then seeing it go away in the action). E.g.

generate:
    ...
    poetry run black .