Merge branch 'feature/multiple-order-prevention' into 'develop'

...kout/stripe_checkout/management/commands/processevents.py

...ut/migrations/0008_order_created_alter_order_stripe_id.py

stripe_checkout/stripe_checkout/models.py

stripe_checkout/stripe_checkout/shopping_cart.py

stripe_checkout/stripe_checkout/static/main.css

stripe_checkout/stripe_checkout/stripe_.py

..._checkout/stripe_checkout/templates/checkout-pending.html

stripe_checkout/stripe_checkout/templates/checkout.html

stripe_checkout/stripe_checkout/visit_views.py

test/conftest.py

test/test_processevent.py

test/test_shopping_cart.py

test/test_visit.py