UpdateSettingsForm::submitForm

public UpdateSettingsForm::submitForm(array &$form, FormStateInterface $form_state)

public function submitForm(array &$form, FormStateInterface $form_state) {
  $config = $this->config('update.settings');
  // See if the update_check_disabled setting is being changed, and if so,
  // invalidate all update status data.
  if ($form_state->getValue('update_check_disabled') != $config->get('check.disabled_extensions')) {
    update_storage_clear();
  }

  $config
  ->set('check.disabled_extensions', $form_state->getValue('update_check_disabled'))
    ->set('check.interval_days', $form_state->getValue('update_check_frequency'))
    ->set('notification.emails', $form_state->get('notify_emails'))
    ->set('notification.threshold', $form_state->getValue('update_notification_threshold'))
    ->save();

  parent::submitForm($form, $form_state);
}