Compatibility crates

New code depends on saml-rs. These three packages re-export the same API.

Package	Import	docs.rs
opensaml	opensaml	docs
samlify	samlify	docs
samlet	samlet	docs

opensaml still exports the deprecated OpenSamlError alias of SamlError. opensaml, samlify, and samlet are maintained with saml-rs.

These packages are separate from Shibboleth OpenSAML and from the Node.js samlify project. samael is the other established Rust SAML crate. It commonly uses the native xmlsec stack.

An integration that still calls the raw types stays on saml_rs::raw. See Raw API.