Fix: PHPize HTTP cache headers

[pspanja]

Q	A
Branch?	main
Tickets	-
License	MIT
Doc PR	-

Building HTTP cache headers in XmlResourceExtractor does not cast read values, which means all values will be strings. In case of eg. s-maxage header, that will result in error since Symfony's Response::setSharedMaxAge(int $value): object expects it to be an integer.

<cacheHeaders>
    <cacheHeader name="shared_max_age">7200</cacheHeader>
</cacheHeaders>

[soyuka]

this should target 4.1

[pspanja]

@soyuka done

[soyuka]

thanks!