This module extends the functionality of point of sale module, to
display on the PoS ticket, the amount of the discount applied for this sale.
Contrary to the logic of Odoo and the OCA
(https://github.com/OCA/sale-workflow/tree/14.0/sale_discount_display_amount)
the amount of the discount is the difference between the theoretical sale with the default price list and the actual sale amount.
So it take into accounts:

- explicit discount set on pos.order.line. (as for odoo ``sale`` module)
- fixed price set on pos.order.line
- discount generated by specific pricelist

Also the module ignores in the computation of undiscounted amount lines, the
lines with a 'Discount Product'.
(see the configure section.)
