BroadcastMessage

{
    "content": "string",
    "from_account_id": "string",
    "offline_enabled": true,
    "ttl": 0,
    "target_os": "string",
    "broadcast_id": "string",
    "create_time": 0,
    "expire_time": 0,
    "client_broadcast_id": "string",
    "sender_id": "string",
    "extension": "string",
    "resend_flag": 0
}