public function merge(Lead $source, Lead $destination): void
    {
        if (empty($source->getId()) || empty($destination->getId())) {
            throw new InvalidParamException('You need to specify two already existing leads in order to merge them');
        }

        $this->client->post($this->prepareUrlForKey('merge-leads'), [], [
            'destination' => $destination->getId(),
            'source' => $source->getId(),
        ]);
    }