mcpg-plugin-identity-saml

SAML 2.0 (Web SSO POST binding) identity plugin for mcpg. Verifies the IdP's XML signature on a SAML Response/Assertion (exclusive-C14N via libxml2 + pure-Rust RSA), validates conditions, and maps attributes to roles/groups. The trust anchor is the operator-configured IdP certificate — never the certificate embedded in the message.