validity
The period during which the codes can be redeemed.
Optional. Without a validity period, the codes stay valid until the list is deactivated.
Both ends are RFC 3339 date-times with a UTC offset, such as 2026-10-01T09:00:00+02:00. A period
that ends before it starts, or an end that is not such a date-time, responds with
InvalidGuestListValidity.
Type
This field resolves to PeriodInput.