### List Books with their current stocks
GET http://localhost:4004/admin/Books?$select=ID,stock

### List all Orders
GET http://localhost:4004/admin/Orders?
&$expand=Items

### Submit Orders
POST http://localhost:4004/browse/Orders
Content-Type: application/json

{ "OrderNo":"2019-09...", "Items":[
    { "book_ID":201, "amount":5 },
    { "book_ID":207, "amount":3 }
]}

# Sending this three times should result in a 409: 5 exceeds stock for book #201