base64url({
  "alg": "ES256",
  "jwk": {
    "crv": "P-256",
    "kty": "EC",
    "x": "hlhwTNi4-7lAOIvf4ykg6db8OPosrocVRwRC14cWg_w",
    "y": "s5Aq1AA6G6aLW4JODyYxOsWtQzVU60XxHT6uOsHdRd0"
  },
  "nonce": "<nonce>",
  "url": "https://letsencrypt.test/new-orderz"
})