public static function paymentRefunded(Purchase $purchase, $amount)
    {
        $purchase->refunded = time();

        $purchase->refundedAmount = $amount;

        $purchase->buyer->sendEmail(
            'You have been refunded',
            'emails.item.refunded',
            [
                'total' => $purchase->refundedAmount,
                'item_name' => $purchase->item->name,
            ]
        );

        $purchase->save();
    }