Function to_https_link 

pub fn to_https_link(
    id: &ConnectionIdentifier,
    domain: &str,
) -> Result<String, String>

Build a domain-hosted HTTPS fallback link: https://<domain>/w#<id.encode()?>.

This is an ordinary https:// URL that works in any browser; on a device where the app has claimed the domain it opens the app instead. The payload rides in the # fragment, which browsers never transmit to the server — so the hosting domain sees only that /w was requested, not the connection payload.