[saml2] keep a reference to the last logged user after slo (for pr@tic)

authentic/liberty/saml2.ptl

@@ -732,7 +732,8 @@ consent_obtained: %s intro_cookie: %s' % (user_authenticated, consent_obtained,
         if not self.check_logout_request(logout):
             return self.slo_sp_finish(logout, method, error = error)
 
-        # logout user now!
+        # logout user now! but remember who was logged.
+        session.previous_user = session.user
         session.user = None
         if method == lasso.HTTP_METHOD_SOAP:
             get_session_manager().expire_session()
@@ -808,6 +809,8 @@ consent_obtained: %s intro_cookie: %s' % (user_authenticated, consent_obtained,
         load_identity(logout, identity = None, session = session)
         if logout.identity:
             session.lasso_identity_dump = logout.identity.dump()
+        # remember who was logged
+        session.previous_user = session.user
         session.user = None
         logout.resetProviderIdIndex()
         if method == lasso.HTTP_METHOD_SOAP:

authentic/sessions.py

@@ -26,6 +26,8 @@ class BasicSession(Session, CaptchaSession, StorableObject):
     __remember = None
     # identifier of the last requesting service
     _service = None
+    # keep reference to the last user logged, after slo for example
+    previous_user = None
 
     _has_info_keys = [ "lasso_login_dump", "lasso_session_dump",
             "question_key", "after_url", "name_identifiers", "proxied_idp",