code: public CorsConfigBuilder exposeHeaders(final CharSequence... headers) {
          for (CharSequence header: headers) {
              exposeHeaders.add(header.toString());
          }
          return this;
      }
docs: Specifies the headers to be exposed to calling clients.
  
  During a simple CORS request, only certain response headers are made available by the
  browser, for example using:
  <pre>
  xhr.getResponseHeader(HttpHeaderNames.CONTENT_TYPE);
  </pre>
  
  The headers that are available by default are:
  <ul>
  <li>Cache-Control</li>
  <li>Content-Language</li>
  <li>Content-Type</li>
  <li>Expires</li>
  <li>Last-Modified</li>
  <li>Pragma</li>
  </ul>
  
  To expose other headers they need to be specified which is what this method enables by
  adding the headers to the CORS 'Access-Control-Expose-Headers' response header.
  
  @param headers the values to be added to the 'Access-Control-Expose-Headers' response header
  @return {@link CorsConfigBuilder} to support method chaining.