curl --request POST \
  --url https://passkeys.hanko.io/{tenant_id}/transaction/initialize \
  --header 'Content-Type: application/json' \
  --header 'apiKey: <apikey>' \
  --data '
{
  "user_id": "<string>",
  "transaction_id": "<string>",
  "transaction_data": {}
}
'

{
  "publicKey": {
    "challenge": "<string>",
    "timeout": 123,
    "rpId": "<string>",
    "allowCredentials": [
      {
        "id": "<string>",
        "transports": []
      }
    ],
    "extensions": {
      "appid": true,
      "appidExclude": true,
      "credProps": {
        "rk": true
      }
    }
  }
}