Allow overriding of default adminsite.

[oyvind]

It would be great to be able to replace the default adminsite in settings.

For example, all contrib apps assume you use the default adminsite.

Would also make it easier for contrib app to just "snap in" another site to add functionality to the admim.

[oyvind]

another possible solution

[Brian Rosner]

Marked #8572 as a duplicate. I think that approach might be better, but certainly a post-1.0 thing.

[oyvind]

Agree that the patch #8572 is better

[Alex Gaynor]

I'm not sure I understand the approach taken there, at present the admin.autodiscover() has no knowledge of the adminsite.

[Jannis Leidel]

updated patch from #8572 by msaelices

[James Bennett]

1.2 is feature-frozen, moving this feature request off the milestone.

[patchhammer]

8500.1.diff fails to apply cleanly on to trunk

[Raffaele Salmaso]

Added a PR => ​https://github.com/django/django/pull/7765

[Raffaele Salmaso]

Hi, I usually override the default admin site with my custom version, then found this ticket, so I choose to complete it.

The first PR was using a new setting (ADMIN_SITE_CLASS), but I rewrote it to use a custom (Simple)AdminConfig and no new setting.
The idea is to delay site instance creation only to when needed with LazyObject, so django.apps can be fully loaded and can access the required attribute.
Using an helper function as the first patch cannot work because require a new setting, and we wanto to avoid that.
This version doesn't require to adapt current code with a

def register(site):
    ...

as the last patch require, or rewriting code not to use django.contrib.admin.sites.site directly.

[Tim Graham <timograham@…>]

In da3df5b8:

Fixed #8500 -- Allowed overriding the default admin site instance.