Use ruff for flake8

Based on !2281 (merged)

I migrated the rules currently, but removed flake8-copyright since we don't have any copyright mentions in our codebase.

arkindex/documents/serializers/entities.py

@@ -31,7 +31,7 @@ class EntityTypeSerializer(serializers.ModelSerializer):
         # Get an error if a request tries to change an entity type's corpus
         corpus = data.get("corpus")
         if self.instance and corpus:
-            raise ValidationError({"corpus": ["It is not possible to update an Entity Type\'s corpus."]})
+            raise ValidationError({"corpus": ["It is not possible to update an Entity Type's corpus."]})
         data = super().to_internal_value(data)
         return data