public function create() : CouponInterface
{
$coupon = new Coupon();
$coupon->setClientUsageLimit(1);
$coupon->setGlobalUsageLimit(1);
$coupon->setModifierType('%');
$coupon->setModifierValue(100);
$coupon->setCode(strtoupper(uniqid()));
$coupon->setCurrency('');
return $coupon;
}