La fonction de suggestion automatique permet d'affiner rapidement votre recherche en suggérant des correspondances possibles au fur et à mesure de la frappe.
Currently, it is not possible to set a file as private via the files API. Your best workaround is to create the file (without setting to hidden == true) via the files API > on the UI > set the file to private > grab the internal file URL > pass it along via the Forms API.
While I couldn't locate an exisiting idea forum, if you haven't already, I'd recommend jumping over to the HubSpot Ideas Forum and posting this idea there so that it's visible to the HubSpot product team and other HubSpot customers and developers. Hopefully this will gather more interest.
It looks like it is showing 404 because there's two file links on the file URL. In this case, I'll have to dig deeper on whether we support submission of multiple files on our Form APIs. I'll keep you posted here!