title: Making Django Readonly ForeignKey Field in Admin Render as a Link
body: <p>I have a model exposed in Django's admin, which uses ModelAdmin's readonly_fields list to show a "user" field, which is a ForiegnKey linking to Django's User model. By default, readonly_fields causes this field to be rendered as simple text containing the user's email (e.g. <code>someuser@domain.com</code>). How would I change this to render as a link to the associated admin page for that user? (e.g. <code>&lt;a href="/admin/auth/user/123/"&gt;someuser@domain.com&lt;/a&gt;</code>)</p>