How can you configure APM with SSO for a 2 stage login, like the new Devcentral page

Add two logon pages one after another. The first logon page with only the username field, the second one with the username and password field but with the username variable set to read only. The field will be populated with the username that has been entered on the first logon page.

SSO will work because the session.logon.last username variable is set on both pages.

Cheers,

Kees