Merge lp://staging/~ricardokirkner/django-openid-auth/custom-user-groups into lp://staging/django-openid-auth

LGTM code-wise, I'm not very knowledgeable on the subtleties of django-openid-auth but this seems to make sense. +1 but maybe you want another review. OTOH this is simple enough that if your tests show it works, we could go ahead.

The explanation was useful to me:

14:42:52 pindonga django.contrib.auth includes User and Group
14:43:02 pindonga and User has a m2m field groups
14:43:22 pindonga django-openid-auth relied on the contrib models so far
14:43:46 pindonga first we allowed for a custom user model, but that would still require that model to include a groups m2m to Group
14:43:54 pindonga sentry's custom user model doesn't have that
14:43:59 pindonga it doesn't use the groups at all
14:44:19 pindonga but to keep d-o-a working like now we do use the group model
14:44:41 pindonga so I though of allowing to customize the <custom user>-group relation by allowing a custom <user, group> mapping table
14:57:39 roadmr pindonga: hm... so in our Sentry's settings you define AUTH_USER_GROUP_MODEL to keep d-o-a happy?
14:57:48 pindonga exactly
14:58:05 pindonga with a custom model provided by sentry_auth_ubuntu_sso (our sso plugin for sentry)

This makes sense and the default behavior to use User.groups.through model is consistent with the explanation.

LGTM :) Thanks!

LGTM