[Seaside] How can I access the authenticated user of a request?

[Avi Bryant]

Ian Prince wrote:

> P.S. on second thought wouldn't access to (say) request cookies be 
> useful for retrieving long-lasting seaside-session-independent user 
> preferences (e.g. retrieving an email address a user had previously 
> entered in a "old" seaside session).

I'm not a big fan of cookies - why not store that stuff server side?  
However, I can see that someone else might want to use them.  My 
inclination, then, would be to have methods on session like #cookieAt: 
and #cookieAt:put:.  These would deal with requests (and responses) 
internally, but they wouldn't make you know anything about which headers 
are used to transmit cookies and so on.