Feature Request: Associate a default credit card per subscription, not per customer record

Problem

For users which have multiple subscriptions, it would be nice to give them an option to designate a default credit card per subscription. This way, different departments for example, could link their default credit card for AutoRenewal.

Proposal

Associate a default credit card per subscription, not per Account.

Relevant Support Tickets

1. https://gitlab.zendesk.com/agent/tickets/132062