Add support for serial number

[kubangab]

Is your feature request related to a problem?
When you select a product from the list there is no way to select what specific serial number the product has

Describe the solution you'd like
After you selected the product and how many you should also be able to add the serial numbers that need to be send in for replacement, repair or refund..

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context about the feature request here.

[pedrobaeza]

The serial number is put on the incoming picking, not on the RMA.

[kubangab]

I understand how it works now. But it would be good if you can enter it already when creating the RMA so that the products that are returned are matched toward the products that is registered before. Also when the mail for return is send to the customer it would be good to include the serial numbers on the return form.

[pedrobaeza]

Yeah, it can be a nice to have, but you have to take into account that the number can be more than 1. Feel free to propose a pull request adding such features.