Dj1.8: repl longerusername with custom user model

The longerusername package is not really compatible with Django 1.7+ - it only
hooks into South migrations, and Django 1.7+ does not allow the "monkeypatch"
approach that longerusername uses to modify the Auth.User model.

Instead, do the proper thing and define a custom user model as per
https://docs.djangoproject.com/en/1.8/topics/auth/customizing/#specifying-a-custom-user-model

To make the transition easy:
* Create a model that inherits from Auth.AbstractUser, only modifying the username length
* Make the model use the auth_user DB table so it picks up existing data
* Call the model User so that links from other existing tables still work

For existing Django 1.4 databases, the model would just inherit the existing table structure.

For new Django 1.8 databases, the generated initial migrations would create the tables the same way.

Make the following considerations in designing and implementing the model:
* Register the model (accounts.User) with the admin class
  (django.contrib.auth.admin.UserAdmin) in accounts/admin.py, not
  accounts/models.py (follow conventions in django.contrib.auth and resolve
  compatibility issues raised in grnet#15).
* Mark the model as swappable.
* Make sure the migration also keeps the swappable property.
* Update imports across the DjNRO codebase to reflect that User is now defined in
  accounts.models, not django.contrib.auth.models - and if possible, in model
  definition, refer to the (swappable) user model through
  settings.AUTH_USER_MODEL.

Swappable models:

The accounts.User Meta class has the same property "swappable" to as is defined in auth.User:

class User(AbstractUser):
    ...

    class Meta(AbstractUser.Meta):
        swappable = 'AUTH_USER_MODEL'

The value of the property is the name of a setting from the Django project's
settings that defines which model class implements a particular feature (the
user model in this case).

With this feature on, only the model class where the name of the class matches
the value of the setting referenced by the property is active.

Without adding this property, and when changing settings.AUTH_USER_MODEL back
to auth.User (either explicitly or by removing the setting and letting it
default to this value), the accounts.User model class would clash with
auth.User - they'd be both adding foreign key relations with the same name to
related classes.

accounts/admin.py

@@ -1,8 +1,9 @@
 from django.contrib import admin
-from accounts.models import UserProfile
-
+from accounts.models import User, UserProfile
+from django.contrib.auth.admin import UserAdmin
 
 class UserPrAdmin(admin.ModelAdmin):
     list_display = ('user', 'institution')
 
 admin.site.register(UserProfile, UserPrAdmin)
+admin.site.register(User, UserAdmin)

accounts/models.py

@@ -1,10 +1,31 @@
 from django.db import models
-from django.contrib.auth.models import User
+from django.contrib.auth.models import AbstractUser
+from django.contrib.auth.admin import UserAdmin
+from django.contrib import admin
+from django.conf import settings
+from django.utils.translation import ugettext_lazy as _
 from edumanage.models import Institution
+import re
 
 
+class User(AbstractUser):
+    class Meta(AbstractUser.Meta):
+        swappable = 'AUTH_USER_MODEL'
+        db_table = 'auth_user';
+        verbose_name = _('user')
+        verbose_name_plural = _('users')
+
+User._meta.get_field('username').max_length = 255
+# try also updating the help_text
+try:
+    help_text = User._meta.get_field('username').help_text._proxy____args[0]
+    if help_text != None:
+	User._meta.get_field('username').help_text = _(re.sub("[0-9]+ characters", "255 characters", help_text))
+except:
+    pass
+
 class UserProfile(models.Model):
-    user = models.OneToOneField(User)
+    user = models.OneToOneField(settings.AUTH_USER_MODEL)
     institution = models.ForeignKey(Institution)
     is_social_active = models.BooleanField(default=False)
 

accounts/views.py

@@ -6,7 +6,7 @@
 from django.shortcuts import render
 from django.template.loader import render_to_string
 from django.utils.translation import ugettext_lazy as _
-from django.contrib.auth.models import User
+from accounts.models import User
 from django.views.decorators.cache import never_cache
 from django import forms
 from registration.models import RegistrationProfile

djangobackends/ldapBackend.py

@@ -3,7 +3,8 @@
 
 import ldap
 
-from django.contrib.auth.models import User, UserManager, Permission, Group
+from django.contrib.auth.models import UserManager, Permission, Group
+from accounts.models import User
 from django.conf import settings
 
 class ldapBackend:

djangobackends/shibauthBackend.py

@@ -1,7 +1,8 @@
 # -*- coding: utf-8 -*- vim:encoding=utf-8:
 # vim: tabstop=4:shiftwidth=4:softtabstop=4:expandtab
 
-from django.contrib.auth.models import User, UserManager, Permission, Group
+from django.contrib.auth.models import UserManager, Permission, Group
+from accounts.models import User
 from django.conf import settings
 
 class shibauthBackend:

djnro/settings.py

@@ -39,6 +39,9 @@
     ('en', _('English')),
 )
 
+# Use a custom user model (as replacement for longerusername)
+AUTH_USER_MODEL = 'accounts.User'
+
 # Language code for this installation. All choices can be found here:
 # http://www.i18nguy.com/unicode/language-identifiers.html
 LANGUAGE_CODE = 'en'
@@ -150,7 +153,6 @@
 )
 
 INSTALLED_APPS = (
-    'longerusername',
     'django.contrib.auth',
     'django.contrib.contenttypes',
     'django.contrib.sessions',

edumanage/decorators.py

@@ -1,7 +1,7 @@
 from django.template import RequestContext
 from django.shortcuts import render
 from django.utils.translation import ugettext as _
-from django.contrib.auth.models import User
+from accounts.models import User
 from django import forms
 
 from accounts.models import UserProfile

edumanage/management/commands/contacts.py

@@ -12,7 +12,7 @@
 
 from optparse import make_option
 from django.core.management.base import BaseCommand
-from django.contrib.auth.models import User
+from accounts.models import User
 
 
 class Command(BaseCommand):

edumanage/models.py

@@ -7,7 +7,6 @@
 from django.utils.text import capfirst
 from django.core import exceptions
 from django.conf import settings
-from django.contrib.auth.models import User
 from django import forms
 from django.core.exceptions import ValidationError
 
@@ -582,7 +581,7 @@ class CatEnrollment(models.Model):
     inst = models.ForeignKey(Institution)
     url = models.CharField(max_length=255, blank=True, null=True, help_text="Set to ACTIVE if institution has CAT profiles")
     cat_instance = models.CharField(max_length=50, choices=settings.CAT_INSTANCES)
-    applier = models.ForeignKey(User)
+    applier = models.ForeignKey(settings.AUTH_USER_MODEL)
     ts = models.DateTimeField(auto_now=True)
 
     class Meta:

edumanage/views.py

@@ -29,7 +29,7 @@
 from django.views.decorators.cache import never_cache
 from django.utils.translation import ugettext as _
 from django.contrib.auth import authenticate, login
-from django.contrib.auth.models import User
+from accounts.models import User
 from django.core.cache import cache
 from django.contrib.auth import REDIRECT_FIELD_NAME
 

requirements.txt

@@ -3,7 +3,6 @@ argparse>=1.2.1
 django-registration==2.0.4
 django-tinymce==1.5.3
 ipaddr==2.1.11
-longerusername==0.4
 python-social-auth==0.2.14
 requests==2.7.0
 wsgiref==0.1.2