Sending content warnings

[robintown]

MSC3286 proposes a way to tag image, video, audio, and file messages as spoilers. Users need to have a way to mark these kinds of messages as a spoiler on upload, and optionally provide a reason for the spoiler.

[BBaoVanC]

UI could just be a simple checkbox on the "Upload files" menu you get when uploading/pasting media. Then maybe a text box could appear when checking that box, which you can optionally type a reason into.

[robintown]

Yep, that's mostly what I was thinking too

[robintown]

This is now MSC3725