feat: Webhook Notification

[davidgrayston-paddle]

Added

Paddle\SDK\Notifications\Notification

Subtypes added in #73

Usage

use Paddle\SDK\Notifications\Notification;

$notification = Notification::fromRequest($request);
$id = $notification->id;
$event = $notification->event;
$eventId = $event->eventId;
$eventType = $event->eventType;
$occurredAt = $event->occurredAt;

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

[davidgrayston-paddle]

Superseded by #74