Merge branch 'feature/product-rest-services' into develop

* Added POST tests and postAction()
* Added DELETE test and deleteAction()
* Changed putAction()
* Fixed ORM description for `AdvancedProduct` by adding the `precision` and `scale` attributes to the `cost` field

- [x] test coverage
- [ ] finish the code
- [x] gather feedback for my changes
- [ ] submit changes to the documentation


| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [yes]
| Tests pass?   | [yes]
| Fixed tickets | [no]
| Doc           | [none]