Need advice: mailbox-based \Seen flag

[Rob Mueller]

> I actually went digging into seen state and cyrus.index a little today
> for another reason, and I realized that we wouldn't have to expand/upgrade 
> the index file to accomodate a shared seen state.  The existing field for 
> system flags is just a bitmask, so we could easily add a bit for shared 
> \Seen.  We could also implement the sharedseen annotation as a mailbox 
> flag in the index header, just like condstore.
>
> Based on other changes that I'm thinking about, I'm starting to like this 
> idea better, even thought it *may* involve more code.

Doesn't that just seem annoying having two *completely* different ways of 
storing seen state? There' probably quite a few places in the code that look 
for the seen state. It just seems much easier to me to have a single flag 
that controls whether to open a specific users seen db, or the "anyone" user 
seen db, rather than having to special case lots of code around the place 
for either pulling from the seen db, or looking up a bit in the index file.

Rob