The maximum time by which the deadline for each incoming message is extended.
While waiting for an ack or nack, The Cloud Pub/Sub C++ client library will extend the deadline by at most this amount. The default extension time is 10 minutes. An application may wish to reduce this extension time so the Pub/Sub service will resend a message sooner when it does not hear back from a Subscriber. With at-least-once semantics, making the time too short may increase the number of duplicate messages delivered by the service.
The value is clamped between 10 seconds and 10 minutes. Note that this option also affects the effective range for MinDeadlineExtensionOption.
