code: public ProxyDataSourceBuilder logSlowQueryBySlf4j(long thresholdTime, TimeUnit timeUnit) {
          return logSlowQueryBySlf4j(thresholdTime, timeUnit, null, null);
      }
docs: Register {@link SLF4JSlowQueryListener}.
  
  @param thresholdTime slow query threshold time
  @param timeUnit      slow query threshold time unit
  @return builder
  @since 1.4.1