Web SSO agent cannot set request user credentials for CMS

In 7.9 there was possible to set a request attribute with a UserCredentials object in order to bypass the login screen:

req.setAttribute(UserCredentials.class.getName(), userState.getCredentials());

This is typically done in a SSO setup and setting this attribute in a filter before the hst filter would allow the user to access the cms without showing the login page.
The following method of class

 org.hippoecm.frontend.session.PluginUSerSession

has a comment which suggests me to use it as I just described

 /** {@link #login()} method invokes this method if there's any <code>UserCredentials</code> object from the request.
     * For example, Web SSO Agent can set a UserCredentials for the user as request attribute.
     */
    protected UserCredentials getUserCredentialsFromRequestAttribute() {
        HttpServletRequest request = ((HttpServletRequest) RequestCycle.get().getRequest().getContainerRequest());
        return (UserCredentials) request.getAttribute(UserCredentials.class.getName());
    }
..

Now, in hippo-10 version, this mechanism doesn't work anymore. Reproduction path (I did extract this reproduction path from a sso project which I'm working on so it might be that is not reproducing the problem):

1. create an archetype project
2. add a filter before the hst which creates dummy credentials:

   public class SSOLoginFilter implements Filter {
    @Override
       public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,ServletException {
   
   SimpleCredentials creds = new SimpleCredentials("editor", "DUMMY".toCharArray());
   req.setAttribute(UserCredentials.class.getName(), creds);
   }
   }
   

3. when hitting /cms, the login screen will appear instead of the cms dashboard