Extend Cart Functionality to Subscription Products

Problem Statement:
Currently, cart functionality does not fully support subscription products. This creates friction in the purchase flow and may prevent users from managing subscription-based items in the same way as regular products. We need to extend the cart experience so subscription products can be added, viewed, updated, and purchased seamlessly.

User Story:
As a customer, I want to add subscription products to my cart and manage them like other products, so that I can complete my purchase smoothly in a single checkout flow.