Submitting orders from external website to Retail via eCom
We have an omnichannel setup. We are developing an integration which submits web orders from an external ecommerce website to Retail via the eCom API checkout process.
The website is calculating shipping and taking payment before submitting the order to eCom. The documented order creation process in eCom requires the following:
- the checkout is created
- the line items are added
- the available shipping methods and payment methods are requested
- the required payment shipping and payment methods are set on the checkout
- the checkout is validated
- the checkout is converted to an order
However this requires the identical payment methods and shipping methods to be created in eCom so that they are available to the checkout (step 3). Is that necessary? Or can I just use the website's shipping/payment calculations and submit these as a generic shipping cost? I see it is possible to use 'id' => 'external' for the shipping / payment method IDs - is that what I need here?
Thanks for any pointers.