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

src/documents/migrations/0020_document_added.py

@@ -1,6 +1,3 @@
-# -*- coding: utf-8 -*-
-from __future__ import unicode_literals
-
 from django.db import migrations, models
 import django.utils.timezone
 
@@ -22,7 +19,9 @@ class Migration(migrations.Migration):
             model_name="document",
             name="added",
             field=models.DateTimeField(
-                db_index=True, default=django.utils.timezone.now, editable=False
+                db_index=True,
+                default=django.utils.timezone.now,
+                editable=False,
             ),
         ),
         migrations.RunPython(set_added_time_to_created_time),