H1514 Wholesale customer without checkout permission can complete purchases

**Summary:** By default, Shopify Wholesale customers are prevented from immediately checking out: {F360280} Instead, a store admin must approve each order before the customer can pay. This restriction can be bypassed, allowing a customer to check out orders without prior approval. This also bypasses any maximum checkout amount that a store can set. ## Steps To Reproduce: 1. As a Wholesale owner, ensure that a customer is disallowed from immediately checking out at https://your-store.myshopify.com/admin/apps/wholesale/admin/shops/x/accounts. 1. As the customer, visit the Wholesale shop and fill your cart with products. 1. Observe that the UI forces the user to submit a purchase order: {F360285} 1. To bypass this restriction, intercept the request to `PUT /purchase_orders/submit` to submit the purchase order and change the url to `/purchase_orders/update_checkout`. 1. Observe that executing the request will allow the customer to proceed through the checkout flow and place the order: {F360296} ## Impact This allows a customer to bypass manual approval restrictions for a Wholesale store and immediately check out.