It looks like someone (!) forgot to talk about the new xmpp-rs 0.4 release post !
xmpp.rs/blog/release-xmpp-0-4/
This is a big article trying to make intelligible many changes including low-level crates included in the project
New website and xmpp.rs v0.4 release | xmpp.rs
xmpp.rs is a Rust crate for building clients and servers for the Jabber/XMPP federated networkxmpp.rs