Overview
The reserve capture flow is used to handle payments using dual message
communication. The funds are first reserved through a call to the Payment
Integrator hosted
reserveFunds
method. If this method synchronously returns SUCCESS it means that the funds
are reserved and can be captured or released. This step is commonly known as an
performing an Auth or Authorization.
Capture funds reservation
The funds can be captured by a call to
asynchronousCaptureFundsReservation.
This will start the process of moving the funds into Google's account.
Cancel funds reservation
Alternatively, the reservation of funds can be canceled with a call to
asynchronousCancelFundsReservation.
This frees the hold on the funds. If a reservation is canceled there is no money
movement. Reservations are automatically canceled after a fixed period of time,
typically seven days. 
Acquirer reference number
If the funds are captured, a ARN (Acquirer Reference Number) is generated. That
value is usually not known to the Payment Integrator until a few days later.
Once the value is known, the Payment Integrator must call the Google hosted
setAcquirerReferenceNumberForCaptureNotification
to provide the ARN to Google. Associating the ARN with this transaction allows
Google to handle disputes and fraud related to this transaction.
Subsequent operations
If the funds are captured, the payment may be refunded by Google with a call to
the Payment Integrator hosted
asynchronousRefund
method. Alternatively, the user or issuing bank can start the chargeback process
which is handled through the dispute flow.