Using update to create new variants

Problem/Motivation

As an administrative user, I require the ability to add new variants with skus onto existing products using the update tempalte

Steps to reproduce

Step 1 - Within the module UI:
-Click "CSV Export/Update"
-Click "Export Products"
-Select all Product Fields and click Export
-Click Download Latest Export

Step 2 - Add variants to the downloaded template:
-Under one of the existing products (ID), create a new line
-Leave the product fields blank (eg. Title, Body, Category)
-On the same line add the variation fields (eg. SKU, Image, Price Currency)
-Save the file

Step 3 - Upload/Update the Product
-Within the module UI, click "CSV Export/Update"
-Click "I have CSV file for update"
-Add your saved file and click upload
-The UI will report "Could not identify variation with {SKU Name}"

Proposed resolution

When doing the actions above either create the variant under the product id, or prompt the user if they would like the variant created