Declare development tools in dependency groups

[brianhelba]

This is recommended by Tox, will make it easier to install tooling into development environments, and perfectly fits the use case outlined by PEP 735.

[brianhelba]

I'm leaving actual runtime requirements for development in the dev extra, instead of putting them in a dependency group, since all the other runtime requirements are already in dependencies.

PEP 735 actually outlines a use case for web applications where a project isn't defined at all, and all requirements are defined in a dependency group (with an arbitrary name like main) instead of project.dependencies. That might be a reasonable move, so we can skip the packaging step entirely, but pip currently doesn't support dependency groups (and they're moving slowly at implementation), so we'll need to wait (or switch entirely to uv).

[danlamanna]

I assume this is the earliest version that supports dependency_groups?

[brianhelba]

Yes: https://tox.wiki/en/latest/config.html#dependency_groups

[brianhelba]

Plus, Tox 4.0 was released in December 2022, so I'm fine to assume nobody is using Tox 3.