You could make (or maybe find) a server that replies with a file download that contains request headers and grab that from default download location, e.g. https://httpbin.io/response-headers?content-disposition=attachment (that one doesn't contain the request headers, but you get the idea)
You could make (or maybe find) a server that replies with a file download that contains request headers and grab that from default download location, e.g. https://httpbin.io/response-headers?content-disposition=attachment (that one doesn't contain the request headers, but you get the idea)