fix(responses): invalidate changed options safely

src/govoplan_poll/backend/capabilities.py

@@ -31,6 +31,7 @@ from govoplan_poll.backend.service import (
     create_poll_invitation,
     decide_poll,
     get_poll,
+    get_poll_response_for_respondents,
     list_poll_responses,
     open_poll,
     poll_result_summary_by_id,
@@ -291,6 +292,27 @@ class SqlPollSchedulingProvider(PollSchedulingProvider):
             raise PollCapabilityError(str(exc)) from exc
         return tuple(_response_ref(response) for response in responses)
 
+    def get_response(
+        self,
+        session: object,
+        *,
+        tenant_id: str,
+        poll_id: str,
+        respondent_ids: Sequence[str],
+        invitation_id: str | None = None,
+    ) -> PollResponseRef | None:
+        try:
+            response = get_poll_response_for_respondents(
+                session,
+                tenant_id=tenant_id,
+                poll_id=poll_id,
+                respondent_ids=tuple(respondent_ids),
+                invitation_id=invitation_id,
+            )
+        except PollError as exc:
+            raise PollCapabilityError(str(exc)) from exc
+        return _response_ref(response) if response is not None else None
+
     @staticmethod
     def _transition(callback, session: object, *, tenant_id: str, poll_id: str) -> PollRef:
         try: