-- AlterTable: tambah jejak admin yang membatalkan trip (Phase 2 admin trip ops).
-- `cancelledByAdminId` nullable — diisi hanya saat actor cancel = ADMIN
-- (organizer cancel tidak mengisi field ini).
ALTER TABLE "Trip" ADD COLUMN "cancelledByAdminId" TEXT;
ALTER TABLE "Trip" ADD COLUMN "cancelledReason" TEXT;

-- AddForeignKey: organizer/admin cancel terjaga referensinya kalau admin
-- nantinya dihapus, set NULL supaya history Trip tidak rusak.
ALTER TABLE "Trip" ADD CONSTRAINT "Trip_cancelledByAdminId_fkey"
  FOREIGN KEY ("cancelledByAdminId") REFERENCES "User"("id")
  ON DELETE SET NULL ON UPDATE CASCADE;