Method add

backend/app/services/sso_service.py:289–295

(field: str, value: str | None)

        seen: set[tuple[str, str]] = set()

        def add(field: str, value: str | None) -> None:
            normalized = (value or "").strip()
            key = (field, normalized)
            if not normalized or key in seen:
                return
            seen.add(key)
            lookup_chain.append(key)

        add("unionid", raw_union_id)
        add("external_id", raw_external_id)