Single Logout should be propagated from SP to IdP

[relaxnow]

SimplSAMLphp, when used as a proxy, does not properly propagate SLO requests from upstream Identity Providers. Received on it's SP endpoint they will simply terminate the SP session.

So in a given setup:

A SLO Request from a Our SP will be propagated to the Their SPs, but a SLO Request from a Their SP will not be propagated to the Our SPs.

See: https://groups.google.com/forum/#!topic/simplesamlphp/4Bm42hYfGjI

[relaxnow]

Unfortunately work on this has halted due to budget constraints. A patch was developed on the master branch (post 1.12, pre 2.0 / 1.13), backported to 1.10 and verified with the IST setup. However it was limited in scope to the current issue and used components which are scheduled for removal in the upcoming version.

Discussion on this can be found here: https://groups.google.com/forum/#!topic/simplesamlphp-dev/atyXnJYIEXw