Refactor comments app to use mixins for comment functionality; update admin interfaces and add historical model fixes

media/mixins.py

@@ -0,0 +1,19 @@
+from django.contrib.contenttypes.models import ContentType
+from django.db.models import QuerySet
+
+class PhotoableModel:
+    """Mixin for models that can have photos attached."""
+
+    def get_photos(self) -> QuerySet:
+        """Get photos for this instance."""
+        from media.models import Photo
+        ct = ContentType.objects.get_for_model(self.__class__)
+        return Photo.objects.filter(content_type=ct, object_id=self.pk)
+
+    def add_photo(self, photo: 'Photo') -> None:
+        """Add a photo to this instance."""
+        from media.models import Photo
+        ct = ContentType.objects.get_for_model(self.__class__)
+        photo.content_type = ct
+        photo.object_id = self.pk
+        photo.save()