PIM-3138: Comments on product

| Q                    | A
| -------------------- | ---
| Bug fix?             | N
| New feature?         | Y
| BC breaks?           | N
| CI currently passes? | Y
| Tests pass?          | Y
| Scenarios pass?      | running
| Checkstyle issues?*  | N
| PMD issues?**        | N
| Changelog updated?   | not yet
| Fixed tickets        | PIM-3142
| Doc PR               |
Add entity class name parameter here and a method createEntity to do a new Comment() ;)
If needed, use a factory