CATALOG-10610: Add custom_url field to POST v3 product 409 error

Author: BC-RSikora

reference/catalog/products_catalog.v3.yml

@@ -597,7 +597,7 @@ paths:
 
         '409':
           description: |
-            `Product` was in conflict with another product. This is the result of duplicate unique values, such as name or SKU; a missing or invalid `category_id`, `brand_id`, or `tax_class id`; or a conflicting `bulk_pricing_rule`.
+            `Product` conflicted with another product. This is the result of duplicate unique values, such as name or SKU; a missing or invalid `category_id`, `brand_id`, or `tax_class id`; or a conflicting `bulk_pricing_rule` or `custom_url`.
           content:
             application/json:
               schema: