code: public RestTemplateBuilder additionalCustomizers(
  			Collection<? extends RestTemplateCustomizer> customizers) {
  		Assert.notNull(customizers, "RestTemplateCustomizers must not be null");
  		return new RestTemplateBuilder(this.detectRequestFactory, this.rootUri,
  				this.messageConverters, this.requestFactorySupplier,
  				this.uriTemplateHandler, this.errorHandler, this.basicAuthentication,
  				append(this.restTemplateCustomizers, customizers),
  				this.requestFactoryCustomizer, this.interceptors);
  	}
docs: Add {@link RestTemplateCustomizer RestTemplateCustomizers} that should be applied
  to the {@link RestTemplate}. Customizers are applied in the order that they were
  added after builder configuration has been applied.
  @param customizers the customizers to add
  @return a new builder instance
  @see #customizers(RestTemplateCustomizer...)