Unique identifier for the visitor that triggered this event.
sessionIdstring
Unique identifier for the session in which this event occurred.
timestampstring date-time required
Timestamp of the event (in UTC).
sentAtstring date-time
Timestamp at which the request is sent (in UTC).
Typically, this value is nearly identical to timestamp. However in some
situations there is latency between when the event occurs and when it is
sent to Unify.