code: public boolean writeHeaders(MuRequest request, MuResponse response, Set<Method> allowedMethods) {
          boolean written = writeHeadersInternal(request, response, null);
          if (written) {
              response.headers().set(HeaderNames.ACCESS_CONTROL_ALLOW_METHODS, getAllowedString(allowedMethods));
          }
          return written;
      }
docs: Adds CORS headers to the response, if neeeded.
  
  @param request        The request
  @param response       The response to add headers to
  @param allowedMethods The methods
  @return Returns true if any Access Control headers were added; otherwise false. (Note: the <code>Vary: origin</code> header is always added.