docx files are common in the edu industry for working on long form documents in an offline setting. We have as a requirement from our users to help support their preferred workflow by starting in docx and moving to HTML once they are ready. This endpoint allows us to preserve workflow of the user without bloating up the front-end payload we send.
This is a more complex scenario because of posting a FormData class as well as streaming and concatenating a file input without the ability to store that streamed data.