Define session as guest before redirecting to login page

[SimonLab]

linked to #31 (comment)

When the application redirect to the login page this means that either the user is not logged in yet and try to access a "private" page or the session/jwt is not valid anymore.
On the second case before redirecting to the login page we need to make sure to update the session to guest.
We can call the logout function before redirecting or we can directly call logout which in turns makes sure to redirect to the login page

[SimonLab]

using Cmd.batch we can first logout then redirect to login page:

                        Http.BadStatus 401 ->
                            -- redirect to login page if not logged in anymore
                            ( { model | error = "Access not authorised" }
                            , Cmd.batch
                                [ Session.logout
                                , Route.replaceUrl (Session.navKey model.session) Route.Login
                                ]