Function null_byte_inject 

pub fn null_byte_inject(header_name: &str) -> String

Inject a null byte into the header name at the midpoint.

Some C-based WAF implementations (modSecurity, native nginx modules) use null-terminated string operations internally. A null byte in the header name causes the WAF to see a truncated name (e.g., Content instead of Content-Type\x00), while the upstream server may parse the full name.