The `cancel` endpoint is called when the user clicks `Close` after the recipient has cancelled the request.

[benschop-it]

If the sender tries to send files to a client and the client cancels the request, this is shown on the UI of the sender and the Cancel button becomes a Close button. However, when the user clicks on the Close button, another cancel request is sent to the client, which is superfluous since the client already canceled the request themselves.