POST /tx HTTP/1.1
Host: server.example.com
Content-Type: application/json
Signature-Input: sig1=...
Signature: sig1=...
Content-Digest: sha-256=...

{
    "access_token": {
        "access": [
            "read"
        ]
    },
    "interact": {
        "start": ["redirect"],
        "finish": {
            "method": "redirect",
            "uri": "https://client.example.net/return/123455",
            "nonce": "LKLTI25DK82FX4T4QFZC"
        }
    },
    "client": "987YHGRT56789IOLK"
}