[Seaside] Displaying a session expiration page

[Michel Bany]

> Once this is done, you will be able to re-implement  
> #handleExpiredRequest: to your liking.
>

Sorry I responded too quickly with something you tried already.
In #handleExpiredRequest: you can build a redirect response to
another application that will show the expiration component.
You can also simply re-implement #expiryPathFor:

HTH,
Michel.