replace c.ServerApp.root_dir by environment variable

[jhgoebbert]

jupyter-ai generates files in the directory set by c.ServerApp.root_dir which might not be writable.
This MR adds the ability to overwrite this location with an environment variable called JUPYTERAI_SAVEDIR

If JUPYTERAI_SAVEDIR it will fall back to c.ServerApp.root_dir but checks if that directory is writeable.
If this is not the case it will take the current working directory without any further checks.

Possible fix for issue #326

[welcome]

Thanks for submitting your first pull request! You are awesome! 🤗

If you haven't done so already, check out Jupyter's Code of Conduct. Also, please make sure you followed the pull request template, as this will help us review your contribution more quickly.

You can meet the other Jovyans by joining our Discourse forum. There is also a intro thread there where you can stop by and say Hi! 👋

Welcome to the Jupyter community! 🎉

[dlqqq]

@jhgoebbert Welcome to Jupyter AI! We’re excited to have you contribute.

Jupyter projects use a library called traitlets for static configuration instead of environment variables. This allows JupyterLab to read from both static configuration files and command line arguments, and is generally preferable over environment variables.

I would recommend that we make root_dir a configurable trait on both LearnChatHandler and GenerateChatHandler, and rename the current root_dir kwarg and instance attribute to server_root_dir as well. root_dir should default to server_root_dir if unspecified.

Let me know if you'd like to implement this change. I'm happy to help.

[krassowski]

While not directly solving this problem, there is a pull requests to traitlets adding an option allowing to configure any traitlet via environment variable:

• Add option to load traitlets values from environement. ipython/traitlets#856

As per ipython/traitlets#99 (comment) it is waiting for reviews from interested users.