Content Attachment Does not Show in Trix Editor when Coming back to Edit Mode

I am trying to add a content attachment as per, https://github.com/basecamp/trix#inserting-a-content-attachment. And that works fine. When the content attachment is added the `trix-editor` content looks like this.


Now when I go back to the edit mode I would like to populate all this content including the content attachment on the editor. For this I pass in all the content to the input element (https://github.com/basecamp/trix#populating-with-stored-content) which looks like,

```

```
But somehow when I pass this the editor seems to strip the iframe;


Is there anything I am missing here? Any help will be greatly appreciated. Please let me know if you need more information. 🤔

The associated PR that I am working on to integrate the content attachments is; https://github.com/opencollective/opencollective-frontend/pull/6042