$country = new Country($owner->getApp()->db);
$country->getUserAction('add')->enabled = false;
$country->getUserAction('delete')->enabled = function (Country $m) {
    return $m->id % 2 === 0;
};
$country->addUserAction('mail', [
    'appliesTo' => Model\UserAction::APPLIES_TO_SINGLE_RECORD,
    'preview' => function (Model $model) {
        return 'here is email preview for ' . $model->get('name');
    },
    'callback' => function (Model $model) {
        return 'email sent to ' . $model->get('name');
    },
    'description' => 'Email testing',
]);

// Register a trigger for mail action in Crud
$owner->getExecutorFactory()->registerTrigger(
    ExecutorFactory::TABLE_BUTTON,
    [Button::class, null, 'icon' => 'blue mail'],
    $country->getUserAction('mail')
);
Crud::addTo($owner, ['ipp' => 5])
    ->setModel($country, [$country->fieldName()->name, $country->fieldName()->iso]);