I'm updating some pre-0.7.19 code to current vibe, and I had been
relying on "request.session is null" to check whether a session had been
created.
With the new struct-based Session, is there an equivalent way to check
if I have created a session for the current request? Or is there
always an implicit session and I just have to use a custom session
value like "haveIInitedThisSession_Yet" to accomplish the same thing?