In addition to the new SameSite Servlet Filter described here, a DynamicResponseHeaderFilter callback function has also been implemented (SameSiteCookieHeaderCallbackFunction). The implementation can be found on my personal repository [email@example.com:philsmart/java-support] feature branch [feature/same-site-filter] - alongside the existing Filter implementation. The callback function works in the same way as the filter, but requires less changes to the IdP to deploy.
The function can be configured in global-system.xml, by defining the SameSiteCookieHeaderCallbackFunction bean, and adding it too a new list of response header call backs.
For this to work with application level beans set by the IdP, the DynamicResponseHeaderFilter must be ordered above the CookieBufferingFilter in the web.xml e.g.
It is important to note here, the DynamicResponseHeader filter is intercepting fewer URLs than the current implementation of the SameSite Servlet Filter (which is intercepting all requests to the IdP) - mostly missing SLO endpoints.