function generateBackendOptionsList(settings) {
  const frag = document.createDocumentFragment();

  SettingsController.BACKENDS.forEach(backend => {
    const isChecked = settings.backend === backend.id;
    frag.append(createRadioItem('backend', backend.title, backend.id, isChecked));
  });

  const optionsCategoriesList = dom.find('.options__backend');
  optionsCategoriesList.append(frag);
}
Generates a document fragment containing a list of backends.
@param {SettingsController.Settings} settings