Add possibility to generate and send coupons to abandoned carts automatically

Problem/Motivation

Idea: common use case for webshops for raising conversions is to provide a cheaper option after the customer quits or does not find the total price good enough to submit the order. Mostly one time 5% or 10% coupons are sent for trying to lure back the customer to finish the checkout. There is a module that generates coupons but only after the order was already sent: https://www.drupal.org/project/coupon_after_order → I think the same logic could be used here. The promotion settings enable us to set that the promotion should be used only once per customer, etc.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes