Subscribing a customer to a plan

See this example from tests.apps.example.views.PurchaseSubscriptionView.form_valid

      # Create the stripe Customer, by default subscriber Model is User,
      # this can be overridden with settings.DJSTRIPE_SUBSCRIBER_MODEL
      customer, created = djstripe.models.Customer.get_or_create(subscriber=user)

      # Add the source as the customer's default card
      customer.add_card(stripe_source)

      # Using the Stripe API, create a subscription for this customer,
      # using the customer's default payment source
      stripe_subscription = stripe.Subscription.create(
          customer=customer.id,
          items=[{"plan": plan.id}],
          billing="charge_automatically",
          # tax_percent=15,
          api_key=djstripe.settings.STRIPE_SECRET_KEY,
      )

      # Sync the Stripe API return data to the database,
      # this way we don't need to wait for a webhook-triggered sync
      subscription = djstripe.models.Subscription.sync_from_stripe_data(
          stripe_subscription
      )