Generate documentation for the CS model and settings classes

[chrisburr]

Should be auto generated some how, should be investigated for what the nicest way of handling this is.

[ryuwd]

https://docs.pydantic.dev/latest/api/config/#pydantic.config.ConfigDict.use_attribute_docstrings can be used - available in pydantic 2.7 and above

[chrisburr]

https://github.com/radeklat/settings-doc?tab=readme-ov-file looks interesting, also for #664

[ryuwd]

We will investigate https://mkdocstrings.github.io/griffe-pydantic/#with-extension for documenting the CS in #696

settings-doc for the settings classes with jinja templates (see #698)