Why does butler fetch require authentication for public games

[fanmanpro]

We're looking for a way to download a specific channel and version of a game using butler.

The closest solution seems to be butler fetch <user/project:channel> <destination>, however this always prompts to authenticate. Seen in code here:

butler/cmd/fetch/fetch.go

Lines 60 to 63 in e020453

	client, err := ctx.AuthenticateViaOauth()
	if err != nil {
	return err
	}

I'm curious if there could be a check to first determine if the game is private and only then prompt to authenticate?

Happy to run with the PR if it checks out design wise.

[fasterthanlime]

Downloading via the API always requires an API key (so, authentication), so that we can monitor usage and, if needed, shut down abuse.

We allow downloading free games via the website without an account because we're happy with folks visiting the site, and we're able to recommend them other games, etc.

We provide a platform that graciously offers downloads for free games as long as they're downloaded via the website or our application. We do not offer a free, unlimited, white label CDN :)