feat(core): define auditable poll response retirement

src/govoplan_core/core/poll.py

@@ -110,6 +110,22 @@ class PollSubmitResponseCommand:
     metadata: Mapping[str, object] = field(default_factory=dict)
 
 
+@dataclass(frozen=True, slots=True)
+class PollResponseRetirementCommand:
+    """Retire live responses while preserving their auditable history.
+
+    Owning modules provide every server-trusted identity that can refer to the
+    participant. Providers must soft-delete matching live responses, retain
+    their answers, and treat an exact ``idempotency_key`` replay as a no-op.
+    """
+
+    respondent_ids: tuple[str, ...] = ()
+    invitation_id: str | None = None
+    reason: str = "participant_removed"
+    idempotency_key: str = ""
+    metadata: Mapping[str, object] = field(default_factory=dict)
+
+
 @dataclass(frozen=True, slots=True)
 class PollOptionRef:
     id: str
@@ -150,6 +166,16 @@ class PollResponseRef:
     answers: tuple[PollAnswerRef, ...] = ()
 
 
+@dataclass(frozen=True, slots=True)
+class PollResponseRetirementRef:
+    """Outcome of an auditable response-retirement request."""
+
+    response_ids: tuple[str, ...] = ()
+    retired_at: datetime | None = None
+    newly_retired_count: int = 0
+    replayed: bool = False
+
+
 @runtime_checkable
 class PollSchedulingProvider(Protocol):
     def create_poll(
@@ -275,6 +301,21 @@ class PollResponseSubmissionProvider(Protocol):
         ...
 
 
+@runtime_checkable
+class PollResponseRetirementProvider(Protocol):
+    """Optional extension for owning modules that remove participants."""
+
+    def retire_responses(
+        self,
+        session: object,
+        *,
+        tenant_id: str,
+        poll_id: str,
+        command: PollResponseRetirementCommand,
+    ) -> PollResponseRetirementRef:
+        ...
+
+
 def poll_scheduling_provider(registry: object | None) -> PollSchedulingProvider | None:
     if registry is None or not hasattr(registry, "has_capability"):
         return None
@@ -289,3 +330,20 @@ def poll_response_submission_provider(
 ) -> PollResponseSubmissionProvider | None:
     provider = poll_scheduling_provider(registry)
     return provider if isinstance(provider, PollResponseSubmissionProvider) else None
+
+
+def poll_response_retirement_provider(
+    registry: object | None,
+) -> PollResponseRetirementProvider | None:
+    """Resolve response retirement without making it mandatory for Poll v1 providers."""
+
+    if registry is None or not hasattr(registry, "has_capability"):
+        return None
+    if not registry.has_capability(CAPABILITY_POLL_SCHEDULING):
+        return None
+    capability = registry.capability(CAPABILITY_POLL_SCHEDULING)
+    return (
+        capability
+        if isinstance(capability, PollResponseRetirementProvider)
+        else None
+    )