There's a description of a possible logout event that is notified via the Idp: ``` By logging out of the global SSO Session. In this case the IdP will notify you on /saml2/{uuid}/slo endpoint (already provided). ``` However, the `SignedOut` event object is completely empty: ``` <?php namespace Slides\Saml2\Events; /** * Class LoggedOut * * @package Slides\Saml2\Events */ class SignedOut { } ``` How is the application supposed to know which session should be terminated?