Optionalcallback_Overwrites the default callback url for delivery receipts for this message The REST URL should be of the form: http://host[:port]/path
Optionalchannel_Optional. A single element array that dictates on what channel should the Conversation API try to send the event. It overrides any default set on the contact. Providing more than one option has no effect.
Optionalevent_Optional. Eventual metadata that should be associated to the event.
Optionalqueue
The ID of the app sending the event.