[dev] check_store_during_coverage = on makes every issueBadge for a
subscription ask the dev mock, during paid coverage too, and bank the
month of a charge it can grant, issued once coverage reaches it. So a
renewal can be watched by hand without waiting a month, and a mock that
forgot the plan after a restart answers ended at once.
Off by default, and refused unless accept_unverified_store_receipts is
on, which is itself refused beside a real store: a real store has not
started its next charge while coverage runs, and asking spends the
quota every subscriber shares.
Run: 011-subscription-tools, slice S3a