ISSUE:7121 - warning when try to create multiple products with the same SKU (product duplication improvement and test)

[ecomchallenger]

ISSUE:7121 - warning when try to create multiple products with the same SKU (Improvement for product duplication and integration tests)

Description

• Improvement for product duplication for admin area, when saving the product by choosing: Save & Duplicate
• Adding a product with the same sku is still not allowed
• Fixes in integration tests

Manual testing scenarios

1. Choose Save & duplicate in admin product edit form. Product should be successfully saved and an edit form with the duplicated product data should be opened (previously it was not possible because of an exception about duplicated sku)
2. Try to add product with already existing product sku (via admin area or api). An exception should be thrown with message about duplicated sku.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[ecomchallenger]

Hi @wokisajn, would You be able to take a look at this PR?

Cheers