Fire an event of the given eventName and pass your eventData onto any callback that may be observing the event. Note: the list of Digium eventNames cannot be fired except by the system.
Object passed to any callbacks listening for this event. eventData can contain a 'callback' property that will be executed when an event named eventName.response (for example, contacts.forwardVM.response) is sent with the same messageId.
Unique ID for the message. If messageId is not specified one will be generated automatically.