'text/plain', 'delivery_mode' => Constants::DELIVERY_MODE_PERSISTENT, ]; public function getProperties(): array { return $this->properties; } public function setPayload($data): self { $this->payload = $data; return $this; } public function payload(): string { return $this->serialize(); } public function serialize(): string { $packer = ApplicationContext::getContainer()->get(Packer::class); return $packer->pack($this->payload); } }