Support for custom user model, and especially USERNAME_FIELD

[ghedsouza]

How feasible would it be to support a custom user model? At least one thing that would have to be updated is that all references to user.username, for example:

https://github.com/Bouke/django-two-factor-auth/blob/d113b80c220bcf62b25d252d5980f02420c8c270/two_factor/views/core.py#L444

would have to be updated to use the USERNAME_FIELD (https://docs.djangoproject.com/en/dev/topics/auth/customizing/#django.contrib.auth.models.CustomUser.USERNAME_FIELD) setting on the user model (for cases where, for example, USERNAME_FIELD=email and there is no "username" attribute).

[Bouke]

Hi @ghedsouza, thanks for your question. I don't think it should be very hard to support custom user models. I think that django-otp (dependency) also supports custom user models, looking at the code. I think it would be a nice feature to add. Would you care to contribute this feature to this package?

[ghedsouza]

@Bouke Sounds good. I'll attempt a fix.