Span decodeOne(ReadBuffer buffer) {
      V1Span v1 = JsonCodec.readOne(new V1JsonSpanReader(), buffer);
      List<Span> out = new ArrayList<>(1);
      V1SpanConverter.create().convert(v1, out);
      return out.get(0);
    }
Corresponds to the Zipkin v1 json format
zipkin/src/main/java/zipkin2/codec/SpanBytesDecoder.java