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Describe the bug
A clear and concise description of what the bug is.

We're trying to populate Fider posts with the body of a corresponding GitHub issue. Most of the GitHub-flavored markdown works as expected, but when we try to embed an image with an externally hosted URL, for example:

![Newsletter demo](https://github.com/user-attachments/assets/0830c860-ec0f-435d-a0bf-d4052baeb26c)

The image displays in the rich text editor, but does not display in the published version of the post.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://demo.fider.io/ and click "Try it out here"
2. Enter the following into the post creation dialog box:

   Test embedded image:
    
   ![Newsletter demo](https://github.com/user-attachments/assets/0830c860-ec0f-435d-a0bf-d4052baeb26c)
   

3. See that the image gets displayed
4. Click "Submit your idea"
5. See that the image is no longer visible
6. Click the three dots then "Edit" on the post
7. See that the image has been replaced with ![](fider-image:)

Expected behavior
A clear and concise description of what you expected to happen.

Ideally Fider, should be able to display the image hosted from GitHub.

If that's not possible then, it shouldn't display the image when creating or editing the post.

Screenshots
If applicable, add screenshots to help explain your problem.

Additional context
Add any other context about the problem here.

I can try to help debug further, but I'm wondering if the image URL is getting sanitized at some point upon posting.

The reason it's important for us to be able to embed markdown images is that we want to populate Fider posts directly from GitHub using the API without having to download and re-upload images manually.