I replaced the custom test setup with the test runner. This should make migrating to mikroorm 6 a lot easier once we do it.
There are few more modules to be done, but I thought the PR is super big already so we can tackle them separately.
Note that there are no or very little test changes, it is mostly the setup around the tests.
**What**
Add missing support for updating countries on the POST /admin/regions/:id route.
Furthermore, the PR refactors how the normalization and validation was handled in both create and update scenarios.
Finally, the PR adds a unique index on the country entity, which ensures at the DB level that we cannot have a duplicate country in the DB for a single region.
