fix: util for calculate cart purchases amount was not multiply price of privilege on amount

internal/utils/tariff.go

@@ -10,7 +10,7 @@ func CalculateCartPurchasesAmount(tariffs []models.Tariff) uint64 {
 			privilegesSum := uint64(0)
 
 			for _, privilege := range tariff.Privileges {
-				privilegesSum += privilege.Price
+				privilegesSum += privilege.Price*privilege.Amount
 			}
 
 			sum += privilegesSum