code: public static void copy(RequestContext src, RequestContext dst) {
          dst.attr(TRACE_CONTEXT_KEY).set(src.attr(TRACE_CONTEXT_KEY).get());
      }
docs: Use this to ensure the trace context propagates to children.
  
  <p>Ex.
  <pre>{@code
  // Ensure the trace context propagates to children
  ctx.onChild(RequestContextCurrentTraceContext::copy);
  }</pre>