code: void addTags(Message<?> message, SpanCustomizer result, MessageChannel channel) {
  		// TODO topic etc
  		if (channel != null) {
  			result.tag("channel", messageChannelName(channel));
  		}
  	}
docs: When an upstream context was not present, lookup keys are unlikely added.
  @param message a message to append tags to
  @param result span to customize
  @param channel channel to which a message was sent