HTTP/1.1 201 Created
 Content-Type: application/json
 Location: https://domain.tld/authz/asdf
 Link: <https://domain.tld/acme/new-cert>;rel="next"
 Link: <https://domain.tld/acme/some-directory>;rel="directory"
 {
   "status": "pending",
   "identifier": {
     "type": "dns",
     "value": "domain.tld"
   },

   "challenges": [
     {
       "type": "http-01",
       "uri": "https://domain.tld/authz/asdf/0",
       "token": "IlirfxKKXAsHtmzK29Pj8A"
     },
     {
       "type": "dns-01",
       "uri": "https://domain.tld/authz/asdf/1",
       "token": "DGyRejmCefe7v4NfDGDKfA"
     }
   ],
   "combinations": [[0], [1]]
 }