code: public CorsServiceBuilder preflightResponseHeader(CharSequence name, Supplier<?> valueSupplier) {
          firstPolicyBuilder.preflightResponseHeader(name, valueSupplier);
          return this;
      }
docs: Returns HTTP response headers that should be added to a CORS preflight response.
  
  <p>An intermediary like a load balancer might require that a CORS preflight request
  have certain headers set. This enables such headers to be added.
  
  <p>Some values must be dynamically created when the HTTP response is created, for
  example the 'Date' response header. This can be accomplished by using a {@link Supplier}
  which will have its 'call' method invoked when the HTTP response is created.
  
  @param name the name of the HTTP header.
  @param valueSupplier a {@link Supplier} which will be invoked at HTTP response creation.
  @return {@link CorsServiceBuilder} to support method chaining.