[WIP] PIM-3131: Sequential product edition

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| Bug fix?             |
| New feature?         |
| BC breaks?           |
| CI currently passes? |
| Tests pass?          |
| Scenarios pass?      |
| Checkstyle issues?*  |
| PMD issues?**        |
| Changelog updated?   |
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| Doc PR               |
I think we have to differenciate instanciation of a new entity and Create part of a CRUD action.
In ProductManager we named it createProduct but if we will use a manager interface soon, imho createEntity method name makes more sense than create (I mean entity as OOP name not doctrine name).
But it requires further thinking.