Add Coupon Code/Name to Subscription by Coupon Export

🔍 Problem Statement

The current Subscriptions by Coupon report export identifies transactions associated with coupon usage but does not include the specific Coupon Code or Coupon Name applied to each transaction. As a result, customers cannot easily determine which coupon campaign generated a particular sale, making coupon performance analysis, campaign attribution, and reporting more difficult.

💡 User Story

As a marketing or subscription manager,
I want the Subscriptions by Coupon report export to include the Coupon Code and/or Coupon Name used for each transaction,
so that I can accurately track sales performance, measure coupon campaign effectiveness, and perform detailed reporting on coupon usage.

🎯 Definition of Done (DoD)

A feature is done when:

✔ Given a transaction associated with a coupon, when the Subscriptions by Coupon report is exported, then the export includes the specific Coupon Code and/or Coupon Name used for that transaction.

✔ A new column for Coupon Code and/or Coupon Name is added to the export file.

✔ The exported coupon information matches the coupon applied at the time of the transaction.

✔ Transactions without a coupon display a blank or appropriate null value in the coupon field(s).