Make an interop test based on a GS1 credential (without trace context).

[Nis Jespersen]

Continued from:
#512

[Nis Jespersen]

Noting that our current interop /issue test also doesn't include trace context - should it?

{
    "credential": {
        "@context": [
            "https://www.w3.org/2018/credentials/v1"
        ],
        "id": "urn:uuid:{{$randomUUID}}",
        "type": [
            "VerifiableCredential"
        ],
        "issuer": "{{credential_issuer_id}}",
        "issuanceDate": "{{$isoTimestamp}}",
        "credentialSubject": {
            "id": "did:example:123"
        }
    },
    "options": {
        "type": "Ed25519Signature2018",
        "created": "{{$isoTimestamp}}"
    }
}

[Benjamin Collins]

Waiting for @nissimsan to open PR.

[Nis Jespersen]

The PR has been around for a while; GS1 just commented, so we should be getting close in this.