Add field types, widgets and formatters to reference AI provider
>>> [!note] Migrated issue
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<!-- Migrated from issue #3515209. -->
Reported by: [josh waihi](https://www.drupal.org/user/188162)
Related to !526 !1165
>>>
<h3 id="summary-problem-motivation">Problem/Motivation</h3>
<p>I'm using ECK to create my own data structures for managing prompts, agents, tools and workflows. I'd like to reference AI providers in these entity types.</p>
<h3 id="summary-proposed-resolution">Proposed resolution</h3>
<p>Add an AI provider reference field, widget and formatter.</p>
<h3 id="summary-remaining-tasks">Remaining tasks</h3>
<h3 id="summary-ui-changes">User interface changes</h3>
<h3 id="summary-api-changes">API changes</h3>
<h3 id="summary-data-model-changes">Data model changes</h3>
issue