Add implementation of gateway that can serve proofs of correct behavior.

[Bren2010]

Dependent PRs:

• ipfs-go-ipfs-core: https://github.com/ipfs/interface-go-ipfs-core/pull/23/commits
• go-unixfs: Add ability to read a file through ProofReader. go-unixfs#70

[Bren2010]

I'm having difficulty figuring out how to update the dependencies. Do you guys handle that, or are there docs somewhere I should have followed?

[magik6k]

I may be missing some context, are there any design issues / discussions related to this?

[Bren2010]

@magik6k No, there are wasn't a design issue. Should I open one?

For context, this is the code for the feature that was announced here: https://blog.cloudflare.com/e2e-integrity/. A browser extension that validates these proofs is here: https://addons.mozilla.org/en-US/firefox/addon/cloudflare-ipfs-validator/.

[Stebalien]

Yes, a design issue discussing what this does, how it works, what the motivation is, etc. would be great.

[Bren2010]

I created #6129. Is there anything else I can help with here?

[jacobheun]

Closing this for now while we figure out the state of #6129. Once that's determined we can resurrect this PR as needed.