-- A token is claimed by the enrolment presenting it, and spent only when that enrolment has
-- written everything it needs (novox/hq 04-ISSUES/083).
--
-- Spending came first and the node's keys after, in another database: a store that went away
-- between the two left a spent token and a node with no key, and the host — which makes new keys
-- on every attempt — could not try again. The claim holds the token for one presenter for a short
-- lease, so an attempt that failed part-way can be made again by the same presenter, and a second
-- presenter cannot interleave with the first.

alter table enrolment_token add column claimed_by text;
alter table enrolment_token add column claimed_until timestamptz;