Document how to set nulls_last=True for admin_order_field/ordering

[Petr Dlouhý]

Django in https://code.djangoproject.com/ticket/30981 added possibility to set nulls_last=True for field ordering in ModelAdmin as:

my_model_admin.admin_order_field = F('field').desc(nulls_last=True)

or

@admin.display(ordering=F('field').desc(nulls_last=True))

but I can't any mention of it at ​https://docs.djangoproject.com/en/4.2/ref/contrib/admin/.
In fact I had to find the original issue I report it to set this up correctly.

Would it be possible to mention all possible values of admin_order_field/ordering in the documentation?

[Mariusz Felisiak]

Thanks for the ticket. #30981 fixed a bug, not added a new feature. All database expressions can be used in ordering and it's not an admin-specific feature. Moreover, docs already explain how to sort NULLs in a few places:

• ​https://docs.djangoproject.com/en/stable/ref/models/expressions/#using-f-to-sort-null-values
• ​https://docs.djangoproject.com/en/stable/ref/models/options/#django.db.models.Options.ordering
• ​https://docs.djangoproject.com/en/stable/ref/models/querysets/#order-by

some of them are reference in the Admin docs. I don't think it's worth mentioning in the next place.