Add useful message on providers page when no provider enabled
>>> [!note] Migrated issue
<!-- Drupal.org comment -->
<!-- Migrated from issue #3498887. -->
Reported by: [unqunq](https://www.drupal.org/user/933228)
>>>
<h3 id="summary-problem-motivation">Problem/Motivation</h3>
<p>On a fresh install the providers page displays the heading `Access denied` and the message `You are not authorized to access this page.` I believe we need the information about installing providers on this page when no provider has been enabled.</p>
<h4 id="summary-steps-reproduce">Steps to reproduce</h4>
<p>Install the AI module on a new Drupal site. Navigate to `admin/config/ai/providers`</p>
<h3 id="summary-proposed-resolution">Proposed resolution</h3>
<p>Instead of `Access denied` display something similar to the message shown on the Default settings page: `/admin/config/ai/settings`<br>
e.g.<br>
<code>There are no providers enabled. Choose a provider from the AI module homepage, add it to your project, then install and configure it on this page. </code></p>
issue