title: How to set up user 'tagging' with Parse
body: <p>I am currently making an app with Parse in which users can upload photos and other users can comment on the photos. I would like to set up a method by which a user can 'tag' another user in a comment, similar to facebook/instagram by typing @username.
  I would like this to then send a notification to the mentioned user, but this can be done easily with Parse push notifications. How would i go about setting up the tag feature? </p>