code: public <T> CorsConfigBuilder preflightResponseHeader(final CharSequence name, final Iterable<T> value) {
          preflightHeaders.put(name, new ConstantValueGenerator(value));
          return this;
      }
docs: Returns HTTP response headers that should be added to a CORS preflight response.
  
  An intermediary like a load balancer might require that a CORS preflight request
  have certain headers set. This enables such headers to be added.
  
  @param name the name of the HTTP header.
  @param value the values for the HTTP header.
  @param <T> the type of values that the Iterable contains.
  @return {@link CorsConfigBuilder} to support method chaining.