title: auth.uid is not working
body: <p>Rule:</p>
  
  <pre><code>{
    "rules": {
      "userdata":{
          "$id":{
  
           ".read": "(auth.uid=='aI2OGxb2pnY58ix5ugZLv0rhZqn2')",
           ".write": "(auth.uid=='aI2OGxb2pnY58ix5ugZLv0rhZqn2')"
  
  
      }
      }
    }
  }
  </code></pre>
  
  <p>Actually my rule is so different. But to confirm that auth.uid is not working for me. I added this into my rules and I got same result (Permission Denied). </p>
  
  <p>And my original uid is also same as given in the above rules.</p>
  
  <p>So are there anything wrong in the rule structure or I'm doing anything wrong in firebase configuaration. </p>
  
  <p>Thanx</p>