Experimental Shared Signals Framework support in Keycloak

Keycloak now offers experimental support for the OpenID Shared Signals Framework 1.0, letting it act as a Shared Signals Transmitter that pushes signed Security Event Tokens about identity events to subscribed receivers. This closes a gap where revoking a session in Keycloak previously did not immediately sign users out of connected SaaS apps, and it also unlocks integration with Apple Business Manager for device state sync.