Hey, I have a problem when i want to user findUnique here :

export const saveSign = async (account: Account, user: User) => {
  try {
    await connectToDatabase();
    const userId = user.id;
    const existingUser = await prisma.user.findUnique({
      where: { userId: userId },
      select: { userId: true },
    });

my schema :

model user {
    id          String @id @default(auto()) @map("_id") @db.ObjectId
    userId      String @unique
    name        String
    email       String
    accessToken String
    tokenType   String
    image       String
    sub         Int
}

do you know why ?