JSON Parameter Description:
User Names to which you want to send a message. Limit 50
List of Group unique identifiers to which you want to send a message. Limit 50
Message Container Object
userNamesare required if you are sending to users or clientGroupIds required if you are sending to groups.
In case of Application Bot calling the API, Of-User-Id header is required. Of-User-Id is the userId of the user on behalf of which application bot wants to send a broadcast message.