title: creating a link that will open facebook messenger and send a message
body: <p>i'm creating a registration code for users to a facebook messenger bot i am writing.
  instead of asking them to open a chat with my bot, and type in the registration code, i would like to provide them a link that will open their facebook messenger on a chat window with my bot, and send the registration code automatically.</p>
  
  <p>i saw a link that opens the chat window (<a href="https://m.facebook.com/messages/compose?ids=USER_ID" rel="noreferrer">https://m.facebook.com/messages/compose?ids=USER_ID</a>) but can't get it to send a message too.</p>
  
  <p>if you know how to do that, or have an alternative suggestion, i would appreciate the help.</p>