Sylius version affected: 2.0

Description
The API request GET /api/v2/shop/products-by-slug/{slug} uses a variable URI named slug. The request actually works fine but the Api Platform web interface that interprets the Open API documentation does not allow you to choose the slug to send in the request and as a result the request cannot be sent correctly.

Steps to reproduce
Open the documentation via the path api/v2/docs and submit the request.

Possible Solution
Add the definition to the corresponding Api Platform resources XML file.