[FIX] sale_coupon: Promotion code removed when adding in shopping cart

Steps to reproduce:
- Create a sale.coupon.program with a discount of 10% and generate coupons for it
- Go on the shop and add a product of 100€ in the cart
- Go in your shopping cart and add a promotion code
- A new line has been created in your cart with a discount of 10€
- Click on "Process to checkout"

Bug:

The discount had been removed from the cart

Technically:

When clicking on button "Process to checkout", the function "recompute_coupon_lines" is called several times.
The second time, in function "_remove_invalid_reward_lines", the valid applied coupon program couldn't be retrieved
due to the sale price of the discount_line_product_id = -1000000 €. The function _filter_on_mimimum_amount filtered
the targted program  because the untaxed_amount of the order was equal to -999900€. So the program._compute_program_amount
was all the time greater than untaxed_amount or untaxed_amount + tax_amount

It s not consistant to set a default value to -1000000 to prevent pricelist strikethrough because in some currencies,-1000000 is not enough.
Now the reward lines are not strikethrough.

X-port/cherry-pick of odoo/enterprise@2748249c0b0674d659a363bae4acbc7b4c230dc7

opw:1957671

addons/sale_coupon/models/sale_coupon_program.py

@@ -101,7 +101,7 @@ class SaleCouponProgram(models.Model):
                 'sale_ok': False,
                 'purchase_ok': False,
                 'invoice_policy': 'order',
-                'lst_price': -1000000,  # Prevent pricelist strikethrough as negative value will always be lower then default 1$
+                'lst_price': 0, #Do not set a high value to avoid issue with coupon code
             })
             program.write({'discount_line_product_id': discount_line_product_id.id})
         return program

addons/website_sale_coupon/views/website_sale_templates.xml

@@ -20,6 +20,9 @@
             <span class="js_quantity text-muted" t-esc="int(line.product_uom_qty)"/>
         </t>
     </xpath>
+    <xpath expr="//del" position="attributes">
+        <attribute name="t-if">not line.is_reward_line</attribute>
+    </xpath>
 </template>
 <template id="sale_coupon_result" inherit_id="website_sale.coupon_form">
     <xpath expr="//form[@name='coupon_code']" position="after">