For context to others: Unless you've been following developments in Rust recently, you may or may not have realised that Rust 1.34 [1] introduced the ability to point Cargo (the Rust package manager) at your own private registry, either self-hosted or managed.

So this is really exciting for anyone looking to privately develop or distribute Rust crates (packaged libraries), or to mirror some portion of crates.io for other reasons (e.g. availability, isolation, modification of public crates, etc.).

[1]: Rust 1.34: https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html