SMPOpenUIButtonDisplayAdapter protocol

Adapter protocol for an extension field that represents a button.

• initWithButtonDisplayModel: method
  Called to initialize the extension with its model.
• model:didChangeButtonImage: method
  Called to inform the adapter that the button's image has changed.
• model:didChangeSelected: 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.