def client_data(typ, challenge)
      JSON.dump(
        challenge: challenge,
        origin: app_id,
        typ: typ
      )
    end
def client_data(typ, challenge)
      JSON.dump(
        challenge: challenge,
        origin: app_id,
        typ: typ
      )
    end
The clientData hash as returned by registration and authentication
 responses.

 typ       - The String value for the 'typ' field.
 challenge - The String url-safe base64 encoded challenge parameter.

 Returns a JSON encoded Hash String.