The code generation process is not documented

[crenshaw-dev]

It seems this repo uses a pretty simple OpenAPI-Generator config to create the client(s).

Perhaps a CONTRIBUTING.md would be the appropriate place for this. It would help folks whose changes rely on modifying the OpenAPI-Generator config itself.

[crenshaw-dev]

Just learned that it's all in the Makefile.

Could still probably use a CONTRIBUTING file, but not as important once you know where the generate code is.