Discount Coupon code support for guest users

[yeumatbeo]

nopCommerce version: 4.6

Steps to reproduce the problem: I've enabled the discount coupon code, and it works well for registered accounts. However, an issue arises with guest users. The problem comes from the function: ApplyDiscountCouponCodeAsync(Customer customer, string couponCode). For guest users, the system doesn’t behave correctly. For example, when guest user A adds a discount coupon code, guest user B will also have the same coupon applied, even though user B hasn't added it themselves. The system can't differentiate between guest users A and B when applying the coupon code.

[AndreiMaz]

@yeumatbeo It cannot be repuniroduced. Each guest has unique customer records (a [Customer] table). And discount codes are saved for the current customer (guest) only

P.S. Already duplicated at https://www.nopcommerce.com/en/boards/topic/100944/discount-coupon-code-support-for-guest-users (please discuss there for more information)