@JsonProperty("samzaSqlRelMsgMetadata")
  public SamzaSqlRelMsgMetadata getSamzaSqlRelMsgMetadata() {
    return samzaSqlRelMsgMetadata;
  }
Creates the SamzaSqlRelMessage from {@link SamzaSqlRelRecord}.
@param samzaSqlRelRecord represents the rel record.
@param metadata the message/event's metadata
samza-sql/src/main/java/org/apache/samza/sql/data/SamzaSqlRelMessage.java