[3792792]x_studio_discount

#Done by RHT on the 07/03/2024
#Reviewed by EMI on the 03/04/2024
#Review:
#911 task:
#Need: to know the discounted amount
for so in self:
  discount = 0
  for line in so.order_line:
    if line.product_id.x_studio_prime:
      discount -= line.price_unit
  so["x_studio_discount"] = discount