Custom Emojis are not converted properly by the convert endpoint

Issue Summary

When inserting custom emojis in dynamic content macros, and converting it to styled view through the REST API, the emoji image will be replaced by a blue star.

Steps to Reproduce

1. Add a dynamic content macro to a page
2. Insert a custom emoji in the macro body
3. Grab the storage format for the macro body
4. Convert it to styled view with /wiki/rest/api/contentbody/convert/styled_view
5. Check the result, the img attribute will have the wrong src url.

Expected Results

The converted styled view refers the correct url as the img src

Actual Results

The converted styled view refers the wrong url

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available