Error message when a coupon code is already in use is not descriptive

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.1.3
• Fix Version/s: 2.1.3, 2.2.0
• Component/s: Digital Merchandise Management → Discounts
• Labels: None
• Severity of Issue: Minor
• Git Pull Request: https://github.com/marco-leo/liferay-portal-ee/pull/1203
• Sprint: FlexSprint11

Assumptions

1. Pricing engine V2.0
2. At least one product

Steps to Reproduce

1. Go to Control Panel → Commerce → Pricing → Discounts
2. Create a discount
3. Enable Coupon Code
4. Define a coupon code, e.g. COUPONCODE1
5. Set the discount to active and publish
6. Create a second discount and define the same discount code as in step 4
7. Try to publish

Expected Behavior

A descriptive error message that tells the user that they can't use that code because it already exists

Actual Behavior

*Error:*Please enter a valid coupon code.
Not helpful in telling the user why it's invalid.

Reproduced On

7.1

Tomcat 9.0.33 + HSQL 2.3.3
marco-leo/liferay-portal-ee:7.1.x git hash f6228ce4798853c4074a36021934c732012b438f