static Span.Builder newBuilder(Span.Builder builder, V1Span source) {
    return builder
        .traceId(source.traceIdHigh, source.traceId)
        .parentId(source.parentId)
        .id(source.id)
        .name(source.name)
        .debug(source.debug);
  }
Allows you to split a v1 span when necessary. This can be the case when reading merged
client+server spans from storage or parsing old data formats.

<p>This type isn't thread-safe: it re-uses state to avoid re-allocations in conversion loops.
zipkin/src/main/java/zipkin2/v1/V1SpanConverter.java