Function https_get_conditional 

pub fn https_get_conditional(
    host: &str,
    path: &str,
    etag: Option<&str>,
    last_modified: Option<&str>,
) -> ConditionalGetResult

Perform a conditional HTTPS GET request using ETag and Last-Modified hints.

When the server responds with 304 Not Modified, the returned body is empty and the cached validators are preserved.

Errors

Returns Error if DNS resolution, socket connection, TLS setup, or the HTTP request fails.