title: Firebase rule that needs to check for value in array (contains() in security rules)
body: <p>How do you check for a value in an array within a firebase rule. I am trying to do something like this:</p>
  
  <pre><code>  root.child('connections/'+auth.uid).child('friends').child(someFriendId).exists()
  </code></pre>
  
  <p>So under the connections node for current user, if someFriendId exists in the friends array, allow access. 'someFriendId' isn't the key for the friends array, that is an auto generated ID from using the firebase push() method.</p>