{
  "rules": {
    "admins": {
      ".read": "auth != null",
      ".write": "false",
      ".validate": "newData.val() !== null && newData.val() !== '' && newData.val() !== 'undefined'"
    },
    "users": {
      ".read": "root.child('admins').child(auth.uid).exists()",
      "$user_id": {
        ".read": "auth.uid === $user_id || root.child('admins').child(auth.uid).exists()",
        ".write": "auth.uid === $user_id || $user_id === null || root.child('admins').child(auth.uid).exists()",
        ".validate": "newData.hasChildren(['displayName', 'provider'])"
      }
    }
  }
}