title: Wordpress special admin menu for a unique user
body: <p>I have a custom menu in my wordpress back office created with this code in the functions.php file :</p>
  
  <pre><code>add_menu_page( 'Volunteers', 'Volunteers', 'edit_pages', 'volunteers.php', '', 'dashicons-groups', 23 );
  </code></pre>
  
  <p>I want to create a user who will access only this page in the back office. In other means, when connected, he only see in the left menu of the back office, the "Volunteers" menu.</p>
  
  <p>How can I do that ?</p>
  
  <p>PS: if it's possible, I want to make this possible without update the menu.php file in the directory wp-admin because this file is reinitialized with the wordpress updates.</p>