code: public RestTemplateBuilder basicAuthentication(String username, String password) {
  		return new RestTemplateBuilder(this.detectRequestFactory, this.rootUri,
  				this.messageConverters, this.requestFactorySupplier,
  				this.uriTemplateHandler, this.errorHandler,
  				new BasicAuthenticationInterceptor(username, password),
  				this.restTemplateCustomizers, this.requestFactoryCustomizer,
  				this.interceptors);
  	}
docs: Add HTTP basic authentication to requests. See
  {@link BasicAuthenticationInterceptor} for details.
  @param username the user name
  @param password the password
  @return a new builder instance
  @since 2.1.0