Switch to custom user model (bug 558514)

[washort]

No description provided.

[magopian]

@davidbgk can you please confirm? If so, maybe we won't need it anymore in the near future?

[magopian]

Wow, thanks @washort this is huge, and greatly simplifies the code, thanks!

A few side notes:

• I believe the fixture modifications aren't complete, as the information previously stored on the User are now lost, instead of stored on the user profile (is_active, is_superuser, last_login...)
• I know it'll ask for numerous other code changes, but I'm wondering if we should take this opportunity to rename UserProfile to be simply User?
• in apps/users/views.py line 509 there's a comment that isn't relevant anymore (talking about not using get_profile)
• a few greps yielded some files that might need a second look:
  • apps/addons/tests/test_commands.py seems to have tests that are always skipped (with references to user.user. Maybe we could just get rid of those (in a future PR?)
  • apps/pages/templates/pages/credits.html has things like user.user__username and user.user__display_name, are those correct?
  • apps/users/management/commands/deduplicate_users.py: I believe this command should be rewritten as it uses the auth_user table
  • apps/users/urls.py had auth_views.User = UserProfile which we might not need anymore now that we're using the custom user?

FYI, there's quite a lot of test failures at the moment on this PR: https://ci-addons.allizom.org/job/olympia-build-branch/51/testReport/

[washort]

Thanks for finding those, I'll update with fixes.