-- Where a mailbox's tasks land.
--
-- Gmail carried this as `project_id` in its settings blob. It belongs to the
-- mailbox, and it is worth having for the ones read over IMAP too: a work mailbox
-- filing into the work project is the obvious thing to want, and the alternative
-- is everything landing in the inbox to be moved by hand.
--
-- Empty means the person's inbox, which is also what an id that no longer names a
-- project they can write to falls back to. Not a foreign key for that reason: a
-- deleted project should quietly stop being the destination, not refuse the delete
-- or take the mailbox down with it.
ALTER TABLE mailboxes ADD COLUMN project_id TEXT NOT NULL DEFAULT '';