final public function createSendableMessage(): string
    {
        $variableHeader = $this->createVariableHeader();
        $this->logger->debug('Created variable header', ['variableHeader' => base64_encode($variableHeader)]);
        $payload = $this->createPayload();
        $this->logger->debug('Created payload', ['payload' => base64_encode($payload)]);
        $fixedHeader = $this->createFixedHeader(strlen($variableHeader . $payload));
        $this->logger->debug('Created fixed header', ['fixedHeader' => base64_encode($fixedHeader)]);

        return $fixedHeader . $variableHeader . $payload;
    }