Values.PutTargetsResultEntrySourceRepresents a target that failed to be added to a rule.
type nonrec t = {targetId : TargetId.t option;The ID of the target.
*)errorCode : ErrorCode.t option;The error code that indicates why the target addition failed. If the value is ConcurrentModificationException, too many requests were made at the same time.
*)errorMessage : ErrorMessage.t option;The error message that explains why the target addition failed.
*)}