How to make usernames not case sensitive?

edit

Taken from here: shopfiber.com/case-insensitive-username-login-in-django/
Add custom proxy to model authentication backend:

class CaseInsensitiveModelBackend(ModelBackend):
    """
    By default ModelBackend does case _sensitive_ username authentication, which isn't what is
    generally expected.  This backend supports case insensitive username authentication.
    """
    def authenticate(self, username=None, password=None):
        try:
            user = User.objects.get(username__iexact=username)
            if user.check_password(password):
                return user
            else:
                return None
        except User.DoesNotExist:
            return None

Once you have the model defined, edit your settings.py and specify “AUTHENTICATION_BACKENDS”.

AUTHENTICATION_BACKENDS = ('myproject.myapp.backends.CaseInsensitiveModelBacke