Update TrustClaim format for use with Holochain generated signatures

[harlantwood]

See https://github.com/trustgraph/trustgraph#create-claims

Write example JSON-LD:

• uses standard JSON-LD signatures
• compatible with HC key/signing format

See https://w3c-ccg.github.io/security-vocab/#Ed25519Signature2020 --

{
  "@context": ["https://w3id.org/security/v1", "http://json-ld.org/contexts/person.jsonld", "https://raw.githubusercontent.com/trustgraph/trustgraph-schema/gh-pages/TrustClaim.jsonld"],   // or maybe just our schema here, which references their schemas?
  "type": "TrustClaim",
  "issuer": "did:key:z6Mko2C7FvL9nNN6Ut1yPcUuEjbJoziDjDmjAJixemPkQBss",
  "issued": "2017-03-04T02:05:07-08:00",
  "claim": {
    "@context": "https://schema.org/",
    "type": "Review",
    "itemReviewed": "did:key:z6MkfXP5Jig4jvF1TiPCWgtacXADXt1bWtUaYKRWasU9B2v2",
    "author": "did:key:z6Mko2C7FvL9nNN6Ut1yPcUuEjbJoziDjDmjAJixemPkQBss",
    "keywords": "programming, Elixir",
    "reviewRating": {
      "@context": "https://schema.org/",
      "type": "Rating",
      "bestRating": 1,
      "worstRating": 0,
      "ratingValue": "0.99",
      "description": "Elixir programming"
    }
  },
  "proof": {
    "type": "Ed25519Signature2018",
    "verificationMethod": "https://w3id.org/people/dave/keys/2",  // hm, what goes here?
    "created": "2021-11-05T03:12:54Z",
    "proofPurpose": "assertionMethod",
    "jws": "eyJhbGciOiJFZERTQSIsImI2NCI6ZmFsc2UsImNyaXQiOlsiYjY0Il19..dXNHwJ-9iPMRQ4AUcv9j-7LuImTiWAG0sDYbRRDDiyAjOV9CUmjLMKiePpytoAmGNGNTHDlEOsTa4CS3dZ7yBg" // TODO actual signature
  }
}

PR to REPLACE our existing JSON LD example on home page with new one in this format.

See also zippy's work on signed claims happ. This probably has what we need.

See also:

• https://github.com/WebOfTrustInfo/rwot9-prague/blob/master/draft-documents/did:hc-method.md#alternate-example
  • Notably uses Ed25519SignatureAuthentication2018

[harlantwood]

probably ignore all of this, buuuuuut in case its useful some verbiage from holofractal:

1. We format the core (immutable) data as a JSON-LD verifiable claim
   • This is composed of required plus optional fields
   • See: https://www.w3.org/TR/vc-data-model/#proofs-signatures
   • See also: https://w3c-ccg.github.io/ld-proofs/#linked-data-signatures
2. We canonicalize the JSON via https://datatracker.ietf.org/doc/html/rfc8785
3. We sign the canonical JSON with the private key of the creator
4. We canonicalize the resulting JSON (including the signature)
5. We hash the JSON to a multihash
6. We redundantly store the NFT to IPFS and its home chain (eg Holochain)