Stripe SCA (#1275)

* Stripe SCA
- Upgrade to latest Stripe API
- Deprecate Stripe Checkout for CC
- Migrate CC payments to Payment Intents

* Move SCA to its own view

* Handle CardErrors for PaymentIntents

* Abilty to handle charge webhooks with PaymentIntents

* Better handling of Stripe References

* Fix Stripe Tests

* Move SCA page into orderlayout; perform iFrame SCA

* Handle disputes and pi-webhooks better, fill more into ReferencedStripeObject

* Optionally pass prefetched PaymentIntent to handle-func

* Fix style

* Send message to window.parent not window.top (widget compatibility)

* More accurate loading message

* Show a cog on sca_return.html. On a good internet connection, you barely see it, but on a bad one…

* Robust error handling

* If it's a method and used like a method, let's actually call it like a method!

* Remove logging statement

* Fix JavaScript interference with other frame events

* Use 4:3 aspect ratio, but at least 600px

* Adjust to django_scopes

src/pretix/static/pretixpresale/scss/main.scss

@@ -88,6 +88,12 @@ body.loading .container {
     filter: blur(2px);
 }
 
+.big-rotating-icon {
+    -webkit-animation: fa-spin 8s infinite linear;
+    animation: fa-spin 8s infinite linear;
+    font-size: 120px;
+    color: $brand-primary;
+}
 #loadingmodal, #ajaxerr {
     position: fixed;
     top: 0;
@@ -121,12 +127,6 @@ body.loading .container {
             float: left;
             width: 150px;
             text-align: center;
-            .big-rotating-icon {
-                -webkit-animation: fa-spin 8s infinite linear;
-                animation: fa-spin 8s infinite linear;
-                font-size: 120px;
-                color: $brand-primary;
-            }
         }
         .modal-card-content {
             margin-left: 160px;