Ability to add a product to an already existing sale from product edit and overview

[stevenvandemoortele]

At the moment you can only add a product to an existing sale by going to that sale and adding the variants.

It would be nice if you could also add a product to a sale from the product edit page
Clicking on the button "add a sale" automaticly creates a new sale.

Same for products on the overview page, you can select multiple products and create a new sale / discount, but there is no option to add them to an existing sale.

[lukeholder]

Thanks for the idea. It's tagged as an enhancement.

[nfourtythree]

Closed by #1177