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

comments/mixins.py

@@ -0,0 +1,17 @@
+from django.contrib.contenttypes.fields import GenericRelation
+
+from .models import get_comment_threads
+
+class CommentableMixin:
+    """
+    Mixin for models that should have comment functionality.
+    Uses composition instead of inheritance to avoid historical model issues.
+    """
+    
+    @property
+    def comments(self):
+        """Get comments helper for this instance."""
+        if self.__class__.__name__.startswith('Historical'):
+            # Historical models delegate to their current instance
+            return self.instance.comments
+        return get_comment_threads(self)