[WIP] PIM-3545 Create json product value denormalizers

| Q                    | A
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| Bug fix?             |
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| BC breaks?           |
| CI currently passes? |
| Tests pass?          |
| Scenarios pass?      |
| Checkstyle issues?*  |
| PMD issues?**        |
| Changelog updated?   |
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| DB schema updated?   |
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| Doc PR               |
The name of the class is AttributeOptionDenormalizer so it's sort of clear that the repository inside should be AttributeOptionRepository - also, there is no other repository here - thus I prefer just `$repository` instead of `$attOptionRepository` (can't use `$attributeOptionRepository` not to exceed the static analysis character limit).