bool scLooksLikeBackendUserId(String? value) {
  final text = value?.trim() ?? "";
  if (text.isEmpty) {
    return false;
  }
  return RegExp(r'^\d{15,}$').hasMatch(text);
}

String? scFirstBackendUserId(Iterable<String?> values) {
  for (final value in values) {
    final text = value?.trim() ?? "";
    if (scLooksLikeBackendUserId(text)) {
      return text;
    }
  }
  return null;
}