message: added kind as field in model for span search
diff: @@ -50,6 +50,7 @@ type TagQuery struct {
  type SpanSearchAggregatesParams struct {
  ServiceName string
  OperationName string
  + Kind string
  MinDuration string
  MaxDuration string
  Tags []TagQuery
  @@ -64,6 +65,7 @@ type SpanSearchAggregatesParams struct {
  type SpanSearchParams struct {
  ServiceName string
  OperationName string
  + Kind string
  Intervals string
  MinDuration string
  MaxDuration string
  