SMPOpenUIDurationDisplayAdapter protocol

Protocol for a field extension representing a display-only duration field.

• initWithDurationDisplayModel: method
  Called to initialize the extension with its model.
• model:didChangeDuration: method
  Called to inform the adapter that the field's underlying value has changed, and it needs to be updated to display the correct value.
• model:didChangeFractionalHour: method
  Called to inform the adapter that the field's underlying value has changed, and it needs to be updated to display the correct value.