Update User Model (#1396)

Current GDPR compliant Private Name attribute is not compatible with multi byte strings, and when encountered it fails and returns an empty string for the name_private attribute.

`substr($last_name, 0, 1)` or just `$last_name[0]` is not multi byte compatible, therefore only solution is to use `mb_substr`.

It also supports encoding definitions like `mb_substr($last_name, 0, 1, 'UTF-8')`

Co-authored-by: Nabeel S <nabeelio@users.noreply.github.com>

app/Models/User.php

@@ -151,7 +151,7 @@ class User extends Authenticatable
         $first_name = $name_parts[0];
         $last_name = $name_parts[$count - 1];
 
-        return $first_name.' '.$last_name[0];
+        return $first_name.' '.mb_substr($last_name, 0, 1);
     }
 
     /**