refactor #determine_order_user helper method
refactor #determine_order_user helper method

There's no behavior change to this. It allows subclasses
to easily override how to determine the user.

pervino/solidus,jordan-brough/solidus,scottcrawford03/solidus,Arpsara/solidus,forkata/solidus,Arpsara/solidus,scottcrawford03/solidus,forkata/solidus,scottcrawford03/solidus,pervino/solidus,scottcrawford03/solidus,jordan-brough/solidus,forkata/solidus,Arpsara/solidus,pervino/solidus,jordan-brough/solidus,Arpsara/solidus,forkata/solidus,jordan-brough/solidus,pervino/solidus