feat: Add optional notification ID to events

[davidgrayston-paddle]

Added

• Support for notification_id on notification events

Usage

use Paddle\SDK\Entities\Event;
use Paddle\SDK\Entities\Transaction;
use Paddle\SDK\Notifications\Events\TransactionUpdated;

$event = Event::fromRequest($request);
$id = $event->notificationId;
$eventId = $event->eventId;
$eventType = $event->eventType;
$occurredAt = $event->occurredAt;

if ($event instanceof TransactionUpdated) {
    $transactionId = $event->transaction->id;
}