Allow widgets to upload files into rooms

[skolmer]

Your use case

What would you like to do?

Allow a widget to upload files into encrypted or unencrypted rooms.

Why would you like to do it?

Our use-case is a Whiteboard Widget where we want to allow users to upload PDF files or Images that can be presented on the whiteboard.

How would you like to achieve it?

An extension of the matrix-widget-api that allows a widget to upload files into encrypted or unencrypted rooms.
These files should not be added to the timeline if possible or the API should allow to the widget to prevent the upload showing up in the timeline.

Have you considered any alternatives?

No response

Additional context

No response

[skolmer]

We just realized that if widgets are able to upload files to encrypted rooms it would also be require to download and decrypt files from encrypted rooms using the matrix-widget-api. So I want to extend this feature request to also enable widgets to download encrypted files using the widget api.

[murlock1000]

A use case for uploading files through the matrix-widget-api we encountered was creating a notice board, that allows users to send automatically formatted messages, including pictures from a html form.