[FIX] sale_coupon: correct discount application values from view
[FIX] sale_coupon: correct discount application values from view

Create a coupon program following these steps:

- Set name
- set 'Discount Apply On' to 'On Specific Product'
- Add specific product
- Set 'Apply Discount' to Fixed price
- Input the fixed price
- Save

Generate a coupon and try to apply it on a quotation.
Error will popup because Not all conditions are met.

The field discount_apply_on (invisible with fixed price) keep the
application "specific_products". Fixing by checking the values in the
backend.

opw-2257783

closes odoo/odoo#51574

Signed-off-by: Nicolas Martinelli (nim) <771435c469f83f6aa9c405ac5e1ed06314a94f2d@odoo.com>

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