Message type indicates what product this event will be used for. In this case, the message_type will be conversation
"conversation"
This event occurs when the user either starts speaking, or stops speaking.
conversation.user.started_speaking
, conversation.user.stopped_speaking
"conversation.user.started_speaking"
This is a unique identifier for a given utterance. In this case, it will be the utterance the user is speaking.
"83294d9f-8306-491b-a284-791f56c8383f"