code: public static void addConstructorArgReference(BeanDefinitionBuilder builder, String beanReference) {
          if (StringUtils.hasText(beanReference)) {
              builder.addConstructorArgReference(beanReference);
          }
      }
docs: Sets the property reference on bean definition in case reference
  is set properly.
  
  @param builder the bean definition builder to be configured
  @param beanReference bean reference to add as constructor arg