Finish support for multiple answers polls

utils/template_filters.py

@@ -206,6 +206,11 @@ def get_actor(url):
         return f"Error<{url}/{exc!r}>"
 
 
+@filters.app_template_filter()
+def poll_answer_key(choice: str) -> str:
+    return _answer_key(choice)
+
+
 @filters.app_template_filter()
 def get_answer_count(choice, obj, meta):
     count_from_meta = meta.get("question_answers", {}).get(_answer_key(choice), 0)