code: @VisibleForTesting
    static String generateTraceSpanName(boolean isServer, String fullMethodName) {
      String prefix = isServer ? "Recv" : "Sent";
      return prefix + "." + fullMethodName.replace('/', '.');
    }
docs: Convert a full method name to a tracing span name.
  
  @param isServer {@code false} if the span is on the client-side, {@code true} if on the
  server-side
  @param fullMethodName the method name as returned by
  {@link MethodDescriptor#getFullMethodName}.