Setup a self-hosted docs.rs for private crate registry

[ZhaoXiangXML]

I'm trying to host the docs of some private crates.

I've found https://forge.rust-lang.org/docs-rs/self-hosting.html but it does not say anything about private registry.

Also according to #1791 it was outdated a year ago?

Is there an up-to-date doc for this matter?

[syphar]

Sadly, there is no up-to-date doc. Feel free to ask any question in zulip, we'll try to help.

The repository for the documentation above is https://github.com/rust-lang/rust-forge/, so

but it does not say anything about private registry

The registry index can be configured using REGISTRY_URL (for the index git repository) and DOCSRS_REGISTRY_API_HOST (for the API endpoint).