code: public static Payload create(String data, @Nullable String metadata) {
      return create(
          ByteBufUtil.writeUtf8(ByteBufAllocator.DEFAULT, data),
          metadata == null ? null : ByteBufUtil.writeUtf8(ByteBufAllocator.DEFAULT, metadata));
    }
docs: Static factory method for a text payload. Mainly looks better than "new ByteBufPayload(data,
  metadata)"
  
  @param data the data of the payload.
  @param metadata the metadata for the payload.
  @return a payload.