im trying to understand why a User and Password model is like this:

model User {
  id    String @id @default(cuid())
  email String @unique

  createdAt DateTime @default(now())
  updatedAt DateTime @updatedAt

  password Password?
  notes    Note[]
}

model Password {
  hash String

  user   User   @relation(fields: [userId], references: [id], onDelete: Cascade, onUpdate: Cascade)
  userId String @unique
}