Cakephp 3 authentication plugin: integration with IdP using SAML (Shibboleth)

Hi, i can not understand how integrate the new authentication plugin with authenticators not listed in documentation.
My company uses Shibboleth for single sign on, and since many years we simply extends Cake\Auth\BaseAuthenticate and AuthComponent for work.

I hope can solve this problem cause we would like to continue using Cake.