Integrate with Django's dumpdata command via natural primary/foreign key

[sergei-maertens]

Currently, when dumping the configuration as fixtures, PKs are included. This may be problematic to share the same fixtures between different projects, or when moving them between staging -> production.

For this, the natural keys approach should be implemented on the models: https://docs.djangoproject.com/en/4.2/topics/serialization/#natural-keys