feat(scheduling): bound public cancellation notices

src/govoplan_scheduling/backend/schemas.py

@@ -316,6 +316,7 @@ class SchedulingRequestResponse(BaseModel):
     calendar_event_id: str | None = None
     handed_off_at: datetime | None = None
     cancelled_at: datetime | None = None
+    cancellation_notice_until: datetime | None = None
     created_at: datetime
     updated_at: datetime
     metadata: dict[str, Any] = Field(default_factory=dict)
@@ -423,6 +424,9 @@ class SchedulingPublicParticipationResponse(BaseModel):
     timezone: str
     status: str
     deadline_at: datetime | None = None
+    cancelled_at: datetime | None = None
+    cancellation_notice_until: datetime | None = None
+    cancellation_notice_only: bool = False
     participant_email_required: bool
     anonymous_password_required: bool
     single_choice: bool