Voxel stock picking secondary unit

This module changes what is sent to Voxel when a stock picking (transfer) is exported. It works together with the Voxel stock picking export and the secondary unit of measure features.

For each line of the picking, the export now checks whether a secondary unit of measure is set on the line and whether that unit has a Voxel code configured:

• If both are present, the quantity sent is the quantity expressed in the secondary unit, and the unit code sent is the Voxel code of that secondary unit.
• If there is no secondary unit, or it has no Voxel code, the export keeps its previous behaviour and sends the standard quantity and standard unit.

There is no new menu, screen, button or report: the change happens automatically inside the existing Voxel picking export template, so users do not need to do anything extra beyond setting the secondary unit and its Voxel code on the products or lines. The module only extends the report template report.edi_voxel_stock_picking_oca.template_voxel_picking through its _get_product_data method, and does not add new models or fields of its own.