code: public CORSConfigBuilder withAllowedHeaders(String... headerNames) {
          Mutils.notNull("headerNames", headerNames);
          return withAllowedHeaders(asList(headerNames));
      }
docs: <p>On preflight OPTIONS requests, specifies which headers are allowed to be sent on the request, aside from the "simple" headers.</p>
  <p>The "simple" headers are <code>Accept</code>, <code>Accept-Language</code>, <code>Content-Language</code>,
  <code>Content-Type</code> (but only with a MIME type of <code>application/x-www-form-urlencoded</code>, <code>multipart/form-data</code>, or <code>text/plain</code>).
  You do not need to specify the simple headers.</p>
  @param headerNames The names of headers to allow, for example <code>Content-Length</code>
  @return This builder