Autodocument vars/features

[MatthewCroughan]

When making additional envvars that control the program/code flow like cac2be7 it is important to consider that it is not automatically documenting itself or making itself known in anyway.

It might be possible to make a rust function that mandates a documentation string, and that could be printed in some way by the program, imagine stardust-xr-server --list-vars. The way --list-vars could be populated is by a function like stardustxr_make_feature which would take a documentation string and env var as arguments, therefore making it impossible to make an envvar lookup that doesn't document itself and make itself known within the code.

[Sntx626]

Should a config struct be introduced that is build from cli args, env vars and config files to solve this?
This struct could easily be (self-) documented and extended. It would also encapsulate all configuration.

[Sntx626]

There are already proven crates that we could use to achive this, i.e. config and figment.

If there's interest for something like it, I'd be willing to implement a draft PR with this feature.