feat: support for session_state (#712)

* add default signature algorithm

* implements session_state in auth_request.go

* add test

* Update pkg/op/auth_request.go

link to the standard

Co-authored-by: Tim Möhlmann <muhlemmer@gmail.com>

* add check_session_iframe

---------

Co-authored-by: Tim Möhlmann <tim+github@zitadel.com>
Co-authored-by: Tim Möhlmann <muhlemmer@gmail.com>

pkg/op/config.go

@@ -30,6 +30,7 @@ type Configuration interface {
 	EndSessionEndpoint() *Endpoint
 	KeysEndpoint() *Endpoint
 	DeviceAuthorizationEndpoint() *Endpoint
+	CheckSessionIframe() *Endpoint
 
 	AuthMethodPostSupported() bool
 	CodeMethodS256Supported() bool