Attempts to complete or advance a pending 3DS 2 transaction. We require merchants to make authenticated
calls to this endpoint in response to certain Spreedly.ThreeDS.Lifecycle events being emitted:
A pending transaction with a required_action of device_fingerprint will fire a trigger-completion
event when the transaction status was updated due to a callback in the cardholder's iFrame or when 10
seconds have elapsed. When this event is received, it is necessary to call complete so that the
latest transaction state can be retrieved in case of a timeout.
A pending transaction with a required_action of challenge will fire a finalization-timeout when
our Spreedly.ThreeDS.Lifecycle stops polling for updates after 10-15 minutes of not receiving a new
status. When this event is received, it is recommended that merchants call complete so that the
transaction state can be updated due to cardholder abandonment or missed callbacks.
Please see our 3DS2 guides for more information and reference implementations.