Option to disable premature media upload

[deepadmax]

Describe the problem

It is generally useful that attached media gets uploaded as soon as it is added. But sometimes, you attach the wrong file or change your mind. Unless you're the admin of your homeserver, that file now remains there until somebody else decides to remove it.

On a lot of other clients, you have to deliberately press a button to confirm that you want to upload a file.

Describe the solution you'd like

I'd like an option under Security for whether to prematurely upload content before you hit send.

It could be enabled by default to maintain current expectations, though one might argue that people expect that files are not in the media repository if one doesn't actively press to send/upload them.

So that you don't have to choose between having it and not having it, when disabled, there could still be a button to the side of each attached file for manually starting the upload before sending.

Alternatives considered

An MSC proposal could be made to add an optional argument to the media endpoint, requiring further confirmation from the client that the media that was uploaded is final and should remain. This would allow clients to benefit from premature uploads while leaving users in better control of what actually is uploaded.

It is an alternative and maybe it should still be proposed, but it isn't a reason to not add this option in the meanwhile.

Additional context

No response