resetConfigFactory example

// Enable update.module if this option was selected.     $update_status_module = $form_state->getValue('enable_update_status_module');
    if (empty($install_state['config_install_path']) && $update_status_module) {
      $this->moduleInstaller->install(['update']);

      // Add the site maintenance account's email address to the list of       // addresses to be notified when updates are available, if selected.       $email_update_status_emails = $form_state->getValue('enable_update_status_emails');
      if ($email_update_status_emails) {
        // Reset the configuration factory so it is updated with the new module.         $this->resetConfigFactory();
        $this->config('update.settings')->set('notification.emails', [$account_values['mail']])->save(TRUE);
      }
    }

    // We precreated user 1 with placeholder values. Let's save the real values.     $account = $this->userStorage->load(1);
    $account->init = $account->mail = $account_values['mail'];
    $account->roles = $account->getRoles();
    $account->activate();
    $account->timezone = $form_state->getValue('date_default_timezone');
    $account->pass = $account_values['pass'];