🐛 Big file upload fails as unknown error with poor UX feedback

Bug Report

Problematic behavior When trying to insert a big video file (>10MB) on docs.numerique.gouv.fr, an unknown error is show to the user.

Expected behavior/code

• Something less cryptic should happen

Steps to Reproduce

1. Download the linked file,
2. Create a new doc on docs.numerique.gouv.fr
3. Drag and drop the file in the docs
4. 💥

Environment

• Docs version: Today's version :)
• Instance url: docs.numerique.gouv.fr

Possible Solution

• Before the upload a check on the file size vs authorized file size should be performed, and the user notified for a nice UX (a link to the doc for embedding the video directly would be great).

Additional context/Screenshots

Nginx rejects the payload with a 413 that is not handled in the frontend currently, I do think it would be nicier to check the file size before upload.