This adds support for setting byproduct quantities as fixed in manufacturing bills of materials. It helps production teams define byproducts more accurately when their output quantity should not scale with the main product quantity.

Task: https://www.odoo.com/web#id=13346&view_type=form&model=project.task&action=327
Pad: https://pad.odoo.com/p/r.GVthtvGe8iPiM5v6