Add new Subscription class used to wrap all the WC subscription related operations
This MR adds a new Subscription class that wraps all WooCommerce subscription related operation.
A summary of the changes is:
- Clean up several modules moving subscription functionality to the new Subscription class.
- Modify all views and commands so they make use of the new Subscription class.
- Remove all SSH VPN configuration parameters.
- Remove all modules used by old subscription logic in Celery tasks.
Heads up as the removal of
ExternalCredit model will trigger
makemigrations on deployment.