Configures ruff as the one stop linter and resolves warnings it raised

src/documents/migrations/0003_sender.py

@@ -1,6 +1,4 @@
-# -*- coding: utf-8 -*-
 # Generated by Django 1.9 on 2016-01-11 12:21
-from __future__ import unicode_literals
 
 from django.db import migrations, models
 from django.template.defaultfilters import slugify
@@ -23,7 +21,8 @@ def move_sender_strings_to_sender_model(apps, schema_editor):
                 DOCUMENT_SENDER_MAP[document.pk],
                 created,
             ) = sender_model.objects.get_or_create(
-                name=document.sender, defaults={"slug": slugify(document.sender)}
+                name=document.sender,
+                defaults={"slug": slugify(document.sender)},
             )