One stored marketing promo grant, for the promo-expiry sweep to reverse (see PromoStore).
The full grant, in CREDIT; the sweep reverses only what the user hasn't already spent.
Reuses the grant posting's txn_ id, so open is idempotent on it.
open
Set true once the unspent remainder is reversed; claimDue skips it thereafter.
claimDue
One stored marketing promo grant, for the promo-expiry sweep to reverse (see PromoStore).