Subscriptions no longer have root orders
Subscriptions no longer have root orders

The subscription no longer needs to be tied directly to the order that
generated it.

Instead, information that the subscriptions requires (shipping address,
payment method) will either be sourced from the associated user,
referenced from the subscription model directly

solidusio-contrib/solidus_subscriptions,solidusio-contrib/solidus_subscriptions,solidusio-contrib/solidus_subscriptions,solidusio-contrib/solidus_subscriptions