Add ability to set product quantity caps per membership plan

The merchant would like to create membership tiers that not only control access to certain products, but also limit the number of products customers can purchase under each plan during a billing cycle. For example, Membership X could allow up to 2 products per month, while Membership Y could allow up to 8. Once a customer reaches that limit, they would no longer be able to purchase additional products until the next cycle.

This feature would make membership plans more flexible by supporting quantity-based restrictions, enabling merchants to manage inventory better and design tiered plans that align with business goals. It would also enhance customer transparency, as members would clearly understand the limits of their plan and avoid unexpected charges or confusion.

If you think having quantity caps for memberships would benefit your store, please upvote this request!