fix/cancel-order (#120)

* fix: adds ability to cancel order

* passing tests

* chore: clean up unused code

packages/medusa-fulfillment-webshipper/src/services/webshipper-fulfillment.js

@@ -236,6 +236,25 @@ class WebshipperFulfillmentService extends FulfillmentService {
       url: link,
     })
   }
+
+  /**
+   * Cancels a fulfillment. If the fulfillment has already been canceled this
+   * is idemptotent. Can only cancel pending orders.
+   * @param {object} data - the fulfilment data
+   * @return {Promise<object>} the result of the cancellation
+   */
+  async cancelFulfillment(data) {
+    const order = await this.client_.orders.retrieve(data.id)
+
+    if (order.attributes.status !== "pending") {
+      if (order.attributes.status === "cancelled") {
+        return Promise.resolve(order)
+      }
+      throw new Error("Cannot cancel order")
+    }
+
+    return this.client_.orders.delete(data.id)
+  }
 }
 
 export default WebshipperFulfillmentService