Allow for custom groupings in Django Admin

[Karim Ouada]

I recently stumbled upon a small issue in my Django project and thought it might be something that could be helpful for other people as well.

I had a Django app and registered my entities in the Django admin. I didn't like the fact that they were all grouped together, so I wanted to separate them into different subcategories. Obviously Django groups those entities by app_name, which I didn't want to change in the models since many things rely on it. So instead I decided to extend the _build_app_dict method in AdminSite to allow for a custom name, as it seems that the app_dict created in that method is only a representation for the UI in the Django admin.

The way it would work is that there is a new optional parameter in the admin.ModelAdmin called group_name and you can specify a group/category that the entities in the Django admin will be grouped in. If you don't specify it then the default is just the app_label.

I would definitely love to contribute back to Django with this small improvement and I know there are quite some threads online where people were looking for such behavior. Let me know if you think that makes sense and could be helpful.

I already created a small PR with a sample implementation:
​https://github.com/ouadakarim/django/pull/1

[Mariusz Felisiak]

Duplicate of #7497 (see also comment).