UIDVALIDITY probably should only be updated when (max) UID is changed for mailbox

[MTRNord]

I think? Need to double check. It may explain the jumpy list in thunderbird.

[MTRNord]

Turns out this can actually be stored until we wrap!

[MTRNord]

Alternatively we can also change it on recycle but since we dont recycle its fine?

This brings also up that we need to ensure that the SERIAL of postgres wraps to 0 or 1 and not to a negative number