Just want to get a confirmation that the custom SSO provider option is
gone in 4.5? I can't seem to find any trace of it in the docs or in the UA?

Have a customer running 4.0.2 that needs X509 login using smart cards
against UA and I don't want to waste time investigating a custom SSO
solution that won't work when they upgrade.

Would X509 login using Access Manager be a supported option in 4.5?
(since 4.5 supports AM and SAML)