Running the crates.io codebase as a mirror to the official crates.io package
repository has always been experimental and was deprecated quite a while ago.
The code to support this mode has been remove from the project at this point.

To not favor any one company/project, we will not give any recommendation
regarding replacements. Feel free to search our
[Discussions](https://github.com/rust-lang/crates.io/discussions) on how to
set up crates.io mirrors using other software.
