Problem getting shibb 2.3.5 to work with workday

[Peter Schober]

* David Massie <dhm24 at georgetown.edu> [2012-02-07 17:13]:
> Workday uses a form of SSO initiated login. Specifically:
> 
> 1. User points browser to workday site: 
> https://www.myworkday.com/usersdomain/login.flex
> 2. Workday redirects the user's browser to: 
> https://local-shibb.mydomain.com/idp/profile/SAML2/Unsolicited/SSO

SP-initiated "IdP-initiated" login?!
How hard can it be to generate a proper SAML2 authenRequest over a
common protocol binding?
-peter