Creates a passkey assertion

curl --request POST \
  --url https://api.contribyard.com/v1/passkey_assertions \
  --header 'Authorization: Bearer <token>'

{
  "response": {
    "mediation": "<string>",
    "publicKey": {
      "challenge": "<string>",
      "extensions": {},
      "allowCredentials": [
        {}
      ],
      "rpId": "<string>",
      "timeout": 123,
      "userVerification": "<string>"
    }
  }
}