Auth route /whoami for nginx subrequest auth, support changing the session cookie domain for that purpose

lib/sso_bsn_web/router.ex

@@ -74,6 +74,12 @@ defmodule SsoBsnWeb.Router do
     delete "/users/log_out", UserSessionController, :delete
   end
 
+  scope "/", SsoBsnWeb do
+    pipe_through [:api, :fetch_session, :fetch_current_user, :require_authenticated_user]
+
+    get "/whoami", UserSessionController, :check_auth
+  end
+
 
   # OIDC
   scope "/oauth", SsoBsnWeb.Oauth do