Implement Stripe sample end points for a SaaS platform

Stripe is the goto for payment for all our SaaS (or otherwise) ideas. Over the years the team at Anomaly has learnt a great deal about their offerings and boast about being a [partner](https://stripe.com/partners/directory/anomaly). Anomaly has collaborated with various businesses to implement complex use cases like Stripe Connect.

The request is to implement reference versions of various typical. use cases to bootstrap SaaS and other projects quicker:
- [ ] How to setup a payment method
- [ ] Make a payment method the default
- [ ] Best practices for handling webhooks and processing them in the background (asyncio and Celery)
- [ ] Start and modify subscriptions
- [ ] One off charges using the API
- [ ] How to use Direct Debit
- [ ] Setup Intents and Payment Intents

Note that part of this requires configuration and use of Stripe elements which will flow onto the web client lab.