Function enforce_if_header_with_backends 

pub async fn enforce_if_header_with_backends(
    if_header: Option<&IfHeader>,
    filesystem: &dyn DavFileSystem,
    lock_system: &dyn DavLockSystem,
    request_path: &DavPath,
    prefix: &str,
    request_scheme: &str,
    request_host: &str,
) -> Result<(), HttpResponse>

Resolves and enforces a parsed WebDAV If header through the canonical backend ports.