Coverage for orders/order_service.py (from tests/orders/test_order_service.py)

OrderService.create_order             71%
OrderService.apply_discounts          38%
OrderService.calculate_tax             0%
OrderService.reserve_stock            55%
OrderService.charge_payment           64%
OrderService.send_confirmation_email   0%
OrderService._render_confirmation      0%
OrderService.cancel_order             22%
OrderService.refund                    0%
OrderService.export_for_finance       80%

tests/orders/test_order_service.py: 46 tests, 6m40s in CI (starts a real stock database container)