I am working on an integration between my app and my store. My app gets notified of new orders via Shopify's webhook.
The order is fulfilled via a third party and my app gets notified with a tracking number when the item is shipped.
I would like to update the order in Shopify(via the API, I have an integration already set up) so that the customer gets notified with the tracking info via email and/or SMS.
I have read through your API-documentation regarding fulfillments and fulfillment orders, but I don't understand how I can implement this functionality without a complex integration involving the carrier(fulfillment service).
What is the easiest approach for my app to notify the customer of the tracking number?