function getWidgetUrl() {
  return '/widget#recaptcha=' + getRecaptchaMode() + '&emailSignInMethod=' +
      getEmailSignInMethod() + '&disableEmailSignUpStatus=' +
      getDisableSignUpStatus() + '&adminRestrictedOperationStatus=' +
      getAdminRestrictedOperationStatus();
}
@return {string} The URL of the FirebaseUI standalone widget.