* Refactor: re-arrange test application
This was triggered by the need to run "python manage.py", which is impossible when serving the whole project in the same directory as is configured in INSTALLED_APPS ("auditlog_tests"). This setup is heavily inspired by other jazzband projects.
* Add check for missing migrations
The `django-jsonfield` module is not maintained anymore and raises some
errors with Django 4.0. So, as a recommendation in this package, and as
Django 2.2 is still maintained, `django-jsonfield-backport` will do the
job for the `JSONField` field.
Ref #43
Ref #334
