This is the supplement to immerda/apps/iapi!56 (merged)
If user goes over quota we report that, also if it goes down.
Also we report any mismtach.
On the edge / relay side in exim we defer emails to such users as early but still after all the other cheap checks as possible.
See https://doc.dovecot.org/configuration_manual/quota/ for background.
This does not yet work for forwards to catch all nor email alias, but for these it's anyway complicated and likely also hard to implement in a meaningful way.
Requires immerda/apps/iapi!56 (merged)