message: fixed isMigrated to boolean
diff: "description": "Last time the rule was updated in ISO8601 format."
  },
  "isMigrated": {
  - "type": "string",
  + "type": "boolean",
  "description": "the value indicating whether this alert rule is migrated.",
  "readOnly": true
  }
  "description": "Last time the rule was updated in ISO8601 format."
  },
  "isMigrated": {
  - "type": "string",
  + "type": "boolean",
  "description": "the value indicating whether this alert rule is migrated.",
  "readOnly": true
  }
  