protected function expectCT(): array
    {
        if (! ($this->config['expect-ct']['enable'] ?? false)) {
            return [];
        }

        $ct = "max-age={$this->config['expect-ct']['max-age']}";

        if ($this->config['expect-ct']['enforce']) {
            $ct .= ', enforce';
        }

        if (! empty($this->config['expect-ct']['report-uri'])) {
            $ct .= sprintf(', report-uri="%s"', $this->config['expect-ct']['report-uri']);
        }

        return [
            'Expect-CT' => $ct,
        ];
    }