[DEMO] Add UPC code to product_created event

[mikesir87]

As a consumer of Kafka events from the catalog service, I would like to have the upc code added to the product_created event so I can have the UPC code of the new product without needing to immediately look it up.

Desired event:

{
  "action": "product_created",
  "id": 123,
  "name": "Sample product",
  "upc": "100000000002",
  "price": 100,
}

(Do not close. Used for demos)