Fix name of login URL reference
Fix name of login URL reference

See https://docs.djangoproject.com/en/3.0/releases/1.8/#passing-a-dotted-path-to-reverse-and-url

Normally (when only using django.contrib.auth) the name of that URL pattern is
just "login", but together with django-registration-redux, it's "auth_login":

See https://github.com/macropin/django-registration/blob/master/registration/auth_urls.py

studentenportal/web,studentenportal/web,studentenportal/web,studentenportal/web,studentenportal/web