Allow downloading items with curl

[migmartri]

To download an artifact from CAS, in addition to being able to do it with the CLI, you can use the /download HTTP endpoint in the control-plane.

If you open the link below in your browser you'll get redirected and the download will start.

https://cp.chainloop.dev/download/sha256:744ffb7e09fca615818a151745ef872903ae79880f966efb805da736369b1d98

but that's not the case if you use curl and authenticate with an API token (new feature #461)

curl -L -H "Authorization: Bearer $API_TOKEN" https://cp.chainloop.dev/download/sha256:744ffb7e09fca615818a151745ef872903ae79880f966efb805da736369b1d98

The result of running that is a mere Your download will begin shortly... but does not redirect and hence the download process never starts.

It's likely that the issue is related to the use of meta-redirect headers, a feature potentially not supported by clients like curl.

[migmartri]

The issue is because the server returns a refresh header to show a message before redirecting to the CAS.

 HTTP/2 302 
< date: Mon, 18 Dec 2023 21:55:24 GMT
...
< refresh: 1;url=https://cas.chainloop.dev/download/sha256:744ffb7e09fca615818a151745ef872903ae79880f966efb805da736369b1d98...

There is a comment explaining the reason for using this kind of redirect as opposed to the regular 302

	// In order ton show a redirect message in the page before the redirection,
	// we need to use a Refresh Header instead of a vanilla redirect (via location change)
	// We want to show a message because in some cases the download will be shown as downloadable and hence
	// the UX for the user is like the browser got stuck

in any case, we need to support clients like curl and maybe, if detected, return 302 directly