instrument property
Instrument identifies the payment method. It is the anti-farming key: one redemption per instrument, fleet-wide, and it is REQUIRED — an absent instrument is refused, never waved through.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? instrument;