meta=eof+json update

[patrickwoodhead]

Updated the Trustless Gateway doc and IPIP-431 doc based on the discussion in ipfs#431

Of note, the signature is over all other fields so that it is generic enough for other use cases and can be included in the trustless gateway spec.

There is s till a contentious point about whether b3checksum is generic enough to be included in the top level spec, outside of just the scope of Spark

[bajtos]

Great improvements, @patrickwoodhead!

I have a few comments to discuss.

We will also need to add more content to "Security" and "Alternatives" sections to capture the discussion we had in the PR.

[patrickwoodhead]

@bajtos I have had a go at resolving all of your feedback. Please take another look when you can. One thing to note is that the content type for the metadata block in this PR is json, not dag-json. I want to make sure that is the right approach as most of the discussion in the original PR refers to dag-json. I'm just not sure I understand what it gives us here over normal json.

[bajtos]

I have had a go at resolving all of your feedback.

🤩 Awesome, I'll take a look!

One thing to note is that the content type for the metadata block in this PR is json, not dag-json. I want to make sure that is the right approach as most of the discussion in the original PR refers to dag-json. I'm just not sure I understand what it gives us here over normal json.

As I understand it, dag-json is adding few more restrictions & interpretation rules on top of regular JSON.

• Docs: https://ipld.io/docs/codecs/known/dag-json/
• Spec: https://ipld.io/specs/codecs/dag-json/spec/

Most simple JSON objects are valid DAG-JSON. The primary differences are:

• Bytes and Links are supported with special use of single-key ("/") map.
• In limited cases, maps with the key "/" other than those used to encode Bytes and Links, are disallowed.
• Maps are sorted by key.

I think changing the spec from JSON to DAG-JSON is easy, so this is something we can discuss with other IPIP reviewers in the original pull request.