Re-triggering Authorization Flow If Refresh Token Is Expired

If the refresh_token has expired (or the user has - for example - changed password/logged out everywhere, via the IdP), this is not handled correctly.

I also can't find a documented way to re-trigger the authorisation flow/re-show the login prompt.

Instead, the `client.request.invokeTemplate` method throws an Error that contains the "invalid_token" error. 