Pass request object when calling "authenticate".
Pass request object when calling "authenticate".

Cf.:

- https://docs.djangoproject.com/en/2.1/releases/1.11/#django-contrib-auth,
- https://docs.djangoproject.com/en/2.1/releases/1.11/#id2

authenticate() now passes a request argument to the authenticate() method of authentication backends.
Support for methods that don’t accept request as the first positional argument will be removed in Django 2.1.

open-craft/django-lti-tool-provider