docs: @Bean Tracing tracing(
        @Lazy Reporter<Span> reporter, @Value("${zipkin.self-tracing.sample-rate:1.0}") float rate) {
      return Tracing.newBuilder()
          .localServiceName("zipkin-server")
          .sampler(rate < 0.01 ? BoundarySampler.create(rate) : Sampler.create(rate))
          .currentTraceContext(currentTraceContext())
          .spanReporter(reporter)
          .build();
    }