title: Update Twilio chat message body and attribute and get read/unread message counter using iOS sdk
body: <p>1) How we can update Twilio chat message body and attribute using iOS sdk?
     We need to edit message attributes after message sent so is this possible to edit message body by iOS sdk. I found update message body thind api doc for php but not for iOS so please help to do this.</p>
  
  <p>2) How we can get Messages counter for read and unread messages for a User or channel?</p>