title: Social framework returns "(#803) Cannot query users by their username (username)" when trying to get user feed
body: <p>I'm using iOs social framework in order to retrieve facebook feeds from a certain user.
  For that purpose, after authenticating I'm doing the following:</p>
  
  <pre><code>NSURL *requestURL = [NSURL URLWithString:@"https://graph.facebook.com/username"];
  SLRequest *request = [SLRequest requestForServiceType:SLServiceTypeFacebook requestMethod:SLRequestMethodGET
                                                    URL:requestURL parameters:nil];
  request.account = self.facebookAccount;
  
  [request performRequestWithHandler:^(NSData *data, NSHTTPURLResponse *response, NSError *error) { ... }];
  </code></pre>
  
  <p>The response returns:</p>
  
  <pre><code>error =     {
          code = 803;
          message = "(#803) Cannot query users by their username (username)";
          type = OAuthException;
      };
  </code></pre>
  
  <p>The same works if I use <code>/me</code> instead of the username, but I want to retrieve someone else public feed. </p>
  
  <p>I also tried using the user's id which also works for my user, but I it doesnt work for other users, the request returns the following:</p>
  
  <pre><code>code = 2500;
          message = "The global ID 100008339709776 is not allowed. Please use the application specific ID instead.";
          type = OAuthException;
  </code></pre>
  
  <p>I also tried passing the access token as parameter but the behavior is the same.</p>
  
  <p>Any ideas?</p>