feat: Pos invoice coupon code feature

[nemesis189]

Description:

• This feature allows you to apply a coupon code created through the existing Coupon Code doctype at the POS checkout screen.
• Lets you type in the coupon code and a dropdown of relevant coupons will pop up.

Steps:

1. Create a pricing rule for 'Selling' such as the following:

**If the 'Apply On' field has item group selected, add a subsequent item group in the table, same for other options too. The discount will be applicable only for those items which come under the applied option, here its Item Group - POS test items, so items with POS test items as their 'Item Group' only will have this applied.**

2. Create a Coupon Code

3. Select the created coupon code at the POS screen

no-docs

[coveralls]

Coverage increased (+0.05%) to 51.38% when pulling a9c6086 on nemesis189:pos-invoice-coupon-code-feature into 9e82c24 on frappe:develop.

[sagarvora]

Why hasn't the modified timestamp been updated? Did you modify pos_invoice.json directly?

[nemesis189]

Why hasn't the modified timestamp been updated? Did you modify pos_invoice.json directly?

No, I didn't touch the json file

[nextchamp-saqib]

Why hasn't the modified timestamp been updated? Did you modify pos_invoice.json directly?

I gues due to this 086053d, while resolving conflicts, modified timestamp is the latest one though. Will it cause a problem? @sagarvora

[sagarvora]

@nextchamp-saqib Yes, this will cause an issue. The DocType only gets synced with ERP if the modified timestamp is newer (not same or older).