Django 2.2 (LTS) is out of support in April 2022

The max supported Django version (listed in setup.py) is 2.2, and 2.2 stops receiving security updates next month (see the bottom of https://www.djangoproject.com/download/ for dates).

I should be able to find some time to put in a MR to support current Django versions this week, unless anyone is already on it. I had a quick look, and it's certainly using URL router APIs removed in Django 4.0. 3.2 should be simple to support at least though.