Add customer facing label to subscriptions

A customer might have multiple subscriptions to the same product. When this is the case it is hard for the customer to distinguish between them.

Request to add a per-subscription customer-facing label (similar to Stripe's metadata.display_name convention).

Use case:
Products
- SomeSaasProduct (Monthly)
- SomeSaasProduct (Annual)

User is managing multiple teams in SaaS product each requiring it’s own subscription. They might subscribe to 2 “SomeSaasProduct (Monthly)”. Once this happens it is impossible for the user to distinguish which subscription is which when trying to manage.

It would be nice to provide the customer facing label in metadata so that when they view their multiple subscriptions they see which is which.