Reserves a call's most before any room, dispatch or model work: the liability is quoted here from the rates and
limits, the customer's side is allocated to lots in the policy's order, and the supplier's side is checked against
the platform's daily cap together with every hold still open, whatever day it was made on. Reservations that reach
that check take it one at a time, on one platform-wide lock, so two on different UTC days never both read the open
liability before either holds. Idempotent per operation.
Reserves a call's most before any room, dispatch or model work: the liability is quoted here from the rates and limits, the customer's side is allocated to lots in the policy's order, and the supplier's side is checked against the platform's daily cap together with every hold still open, whatever day it was made on. Reservations that reach that check take it one at a time, on one platform-wide lock, so two on different UTC days never both read the open liability before either holds. Idempotent per operation.