[React-admin] Reduce technical debt

[bruhnild]

• [ ] Update to the latest version of react-admin (4.16.1 at the moment) https://marmelab.com/react-admin/documentation.html

• [ ] Add unit testing

• [ ] Add cypress testing (to better catch regression)

• [ ] Change react-admin data provider for django-rest-framework as ra-data-drf seems not maintained anymore https://github.com/bmihelac/ra-data-django-rest-framework is recommended at the moment.

• [ ] Use react-admin's baked-in layout components where possible (toolbar for exemple)