Accept request parameter in FasBackend.authenticate
Accept request parameter in FasBackend.authenticate

According to [1.11 release notes][1] and [2.1 deprecation notes][2]
the ModelBackend.authenticate method should/must accept HTTP request
object (which may be `None`) as the first positional argument.
Failure to do so results in the backend being always skipped
in Django 2.1+.

[1]: https://docs.djangoproject.com/en/2.1/releases/1.11/#id2
[2]: https://docs.djangoproject.com/en/2.1/internals/deprecation/#deprecation-removed-in-2-1

misli/django-fas