External authentication and Bonita Portal user existence

In previous versions of Bonita (5.*) there wasn't any need for user accounts to actualy exist in Bonita Portal. What if I don't want to use LDAP/AD authentication but some custom third party authentication mechanism which doesn't expose users through LDAP protocol? How can I overcome the need for user existence within portal?

In 5.* releases Bonita supported authentication mechanisms like Jasig CAS for example. This isn't available in 6.* community editions anymore?