Client session base class and library set up

[aborem]

Closes #4

Creates base class for transfer services. It extends OAuth2Session from requests_oauthlib, which we should use after all since it (alongside its dependency oauthlib) builds out a lot of security features and standardization in how requests are made.

Note there's no data storage baked into the class. This is on purpose since using our data stores should be optional for anyone who has their own solution. I plan on using package extras (i.e., optional-dependencies) for this.

I had to make a few decisions about how to structure the library and dev environment. I think those are all documented below (some, like pytest, are pretty self-evident so I didn't add a justification):

• pytest for testing
• using pylock.toml: standard that aims to replace requirements.txt, recommended by the official python packaging user guide
• type hints (and mypy for type checking): as far as I know, this is pretty standard and makes development and onboarding way faster. I plan on adding a config file for mypy to standardize type checking (Set linting rules and add to dev environment and dependencies #13), but I'm just using the default configs for now
• ruff for linting: using default configs for now, but still need to make config file (Type checking enforcement in dev environment #15)
• To build the library, run commands in my virtual environment, and update pyproject.toml and pylock.toml, I've been using uv, which has been very simple and easy to use. It does maintain a platform specific lockfile (uv.lock), but it can be exported to pylock.toml super easily, which is not platform specific. Anyone else contributing to the library could ignore uv.lock and just use pylock.toml to set up their local environment.

[aborem]

Necessary to expose type hints when other code imports our library. The filename change is misleading: it just thinks it's the same since tests/__init.py was empty before. I deleted it since we don't need tests to be a module.

[lisad]

I've no objection to uv.lock, but I wonder if pylock.toml is needed if uv is supposed to make other packaging tools unneeded?

[aborem]

You need to have uv installed to import from uv.lock, but several packaging tools (pip, PDM, pipenv, etc.) can now read pylock.toml so it's a bit more flexible and probably good to have!