This documentation is outdated. It may no longer apply to recent midPoint versions.
SSO integration in midPoint 4.0 and earlier is unofficial functionality and it is not supported without a special support contract (see below). Therefore this is not part of official midPoint documentation and it is not updated.
MidPoint 4.1 will introduce official support for (some) SSO functionality in midPoint. See Flexible Authentication.
This functionality requires modification of midPoint build, or even modification of midPoint source code. Therefore it is not officially supported - unless the support is explicitly negotiated in subscription.