-- A walk keeps the backups it takes before it asks its first tier (novox/hq ADR 0404 decisions 2 to 4, issue 1065).
--
-- Per machine and module: asked, pending, done or failed, with the backup's own words, and the machines with no backup
-- holder. Read by whoever says the walk (`plan-moved`). Null for a walk that moves nothing a backup protects, and for
-- a walk kept before this.
alter table release_plan add column backups jsonb;