public CorsServiceBuilder preflightResponseHeader(CharSequence name, Iterable<?> values) {
        firstPolicyBuilder.preflightResponseHeader(name, values);
        return this;
    }
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.

@param name the name of the HTTP header.
@param values the values for the HTTP header.
@return {@link CorsServiceBuilder} to support method chaining.
core/src/main/java/com/linecorp/armeria/server/cors/CorsServiceBuilder.java