Manage purchase orders via Coupa API

Steps

1. Generate an API key in Coupa Setup > API Keys, assigning the key the minimum required scopes (e.g., purchase_orders.read, purchase_orders.write); record the key value shown once at creation.
2. All requests use the base URL https://YOUR_INSTANCE.coupahost.com/api and include the headers 'X-COUPA-API-KEY: YOUR_KEY' and 'Accept: application/json'.
3. To list purchase orders GET /api/purchase_orders with query parameters such as status[eq]=issued and created_at[gt]=DATE; results are paginated with a default page size, use the 'page' parameter to advance.
4. To create a purchase order POST to /api/purchase_orders with a JSON body containing at minimum the header fields (supplier, ship_to_address, currency) and a nested order_lines array with description, quantity, and unit_price.
5. To transmit a created order to the supplier, POST to /api/purchase_orders/ID/issue; this triggers the configured transmission method (email, cXML, EDI) in Coupa.