Add custom user model.
Fix go/accounts so that its tests pass.
Reference correct user model from billing.
Reference User model correctly in test utils.
Correctly reference user model from command utils.
Access new user model correctly from base go.base tests.
Add missing date_joined field to custom user model.
Fix unhooking of test profile creation signals.
Add command utilities for retrieving users.
Fix management commands and tests. Add tests for go_assign_tagpools.
Fix channel tests.
Fix router tests.
Fix login in token manager tests.
Remove stray print.
Fix billing references to user model table.
Merge branch 'develop' into feature/issue-746-allow-longer-usernames
Merge branch 'develop' into feature/issue-746-allow-longer-usernames
Clean up GoUser and GoUserManager a bit.
Schema migration to add gouser table.
Add data migration from auth.User to go_base.GoUser.