Add HTTP/3 Host header support for ModSecurity

[AMoo-Miki]

ModSecurity cannot see the Host header in HTTP/3 requests because HTTP/3 uses the :authority pseudo-header, which nginx parses into r->headers_in.server but doesn't add to the headers list.

This commit:

• Adds NGX_HTTP_VERSION_30 case to http_version switch
• Manually extracts Host from r->headers_in.server for HTTP/3 requests
• Adds Host header to ModSecurity transaction before processing other headers

Fixes #305 false positives from OWASP CRS rule 920280 (Missing Host Header) on HTTP/3 connections.

Tested with nginx 1.29.3 and ModSecurity 3.0.13.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[airween]

Hi @AMoo-Miki,

first of all, thank you for your PR.

I am sure that this is a very important step towards being able to handle HTTP/3 requests. But I'm not sure this is the right way.

Please do not misunderstand me, I don't want to reject this PR, but I think we need to discuss how can we handle HTTP/3 headers correctly.

I think adding a header with the name Host so that it is not the host header is not accurate and might be misleading. I mean in case of HTTP/3, the header authority should be added as authority - but I'm not sure that, this is why I think we should discuss that.

Also, please add some tests to this new feature.