Email notification for watched products

Hi everyone.

When a customer watches a product variant, a notification is send whenever any variant or the main product is changed.

How to reproduce:
1.) You have two product variants, a blue pen and a red pen. The blue pen is out of stock.
2.) A customer wants a notification, when the blue pen is available again, and clicks on the watch button.
3.) The customer then watches the main product, and not the variant.
4.) There is a stock-change for the red pen from 5 to 10.
5.) An email notification is send by the cron, and the watch record is removed.

The customer wanted to get an update on the blue pen, but gets an email when the stock of the red pen is updated. It also removes the watch record.

Tobi