Django-admin-csvexport

Added official support for Django 5.0 and 5.1

* Support for Django-4.2
* Follow model relations across apps
(This once was the default but changed unintendend with 4.1 by using the modeltree lib.)

* fixed a permission issue: 10
* use [django-modeltree](https://github.com/thomst/django-modeltree) library

* Added support for django 4.0 and 4.1
* Skipped support for django 1.11, 2.0 and 2.1