Following up on v5 this is another intermediate step that changes the interface.
A major change here is that instead of passing a 'string' to a method and validate that the string is a valid URI, we now pass an AnyURIValue object, drastically reducing the overhead of validating strings multiple times.
Appropriate to use for people who need to generate/parse SAML 2.0 messages/metadata, or use bindings. Still no full replacement for the old v4. We plan to release a full replacement for v4 in v6.1 where we add ServiceProvider/IdentityProvider where you pass all your configuration and metadata and then those classes will do all the heavy lifting to process requests/responses according to the SAML2 specifications.
Until we release a full replacement, we will keep supporting and patching v4