public void convert(V1Span source, Collection<Span> sink) {
    start(source);
    // add annotations unless they are "core"
    processAnnotations(source);
    // convert binary annotations to tags and addresses
    processBinaryAnnotations(source);
    finish(sink);
  }
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