move the stripe-specific code to selene.util

shared/selene/util/payment/__init__.py

@@ -0,0 +1,5 @@
+from .stripe import (
+    cancel_stripe_subscription,
+    create_stripe_account,
+    create_stripe_subscription
+)

shared/selene/util/payment/stripe.py

@@ -0,0 +1,20 @@
+from stripe import Customer, Subscription
+
+
+def create_stripe_account(token: str, email: str):
+    customer = Customer.create(source=token, email=email)
+    return customer.id
+
+
+def create_stripe_subscription(customer_id, plan):
+    request = Subscription.create(
+        customer=customer_id,
+        items=[{'plan': plan}]
+    )
+
+    return request.id
+
+
+def cancel_stripe_subscription(subscription_id):
+    active_stripe_subscription = Subscription.retrieve(subscription_id)
+    active_stripe_subscription.delete()