Flag to identify if user selected SSO or not

[Nate Klingenstein]

> I don’t know how or whether I would go about honoring it, but it’s definitely worth a think.

My first thought is that this could be baffling for users and administrators.  This is effectively trying to do session synchronization without actually doing session synchronization.

Supporting actual single logout would be a requirement for me before I would be willing to support this unless it’s only a brief session.