SAML integration with "request header pre-authentication"

The forum/document says the following: "Appian can authenticate users via other authentication mechanisms (such as Kerberos, request header pre-authentication, central authentication service, or certificate-based authentication) by integrating with a SAML identity provider that uses those mechanisms to authenticate users."

I have an external IdP (must use; can't change) which returns attributes (name, role, etc. ) as http headers. Has anyone implemented a SAML to "request header pre-authentication" model and how did they do so? Any hints, tips, tricks, and or techniques welcome.

Thank you.

OriginalPostID-271449