title: Directus 9, how can I set permissions on Files?
body: <p>I have an App with private messages, the messages are stored in a directus collections, each item has multiple Attachments (files).
  How can I restrict access to these files for other users, that are not in the Conversation?</p>
  <p>I have tried set up a usergroup for each conversation, but I think its not the best way to do it.</p>
  <p>And another question, how can I set the &quot;mine&quot; permission on files?</p>