feat: Event notification sub types

[davidgrayston-paddle]

Added

• Event notification sub types with notification_id

Usage

use Paddle\SDK\Entities\Event;
use Paddle\SDK\Notifications\Notification\TransactionUpdatedNotification;

$notification = Event::notificationFromRequest($request);
$notification_id = $notification->getNotificationId();
$eventId = $notification->eventId;
$eventType = $notification->eventType;
$occurredAt = $notification->occurredAt;

if ($notification instanceof TransactionUpdatedNotification) {
    $transactionId = $notification->transaction->id;
}

[davidgrayston-paddle]

Prevents

- public static function notificationFrom(array $data): Event&NotificationInterface
+ public static function notificationFrom(array $data): self&NotificationInterface

[davidgrayston-paddle]

We cannot have public readonly string $notification_id on the interface, so have added a getter.

[davidgrayston-paddle]

Superseded by #74