How does Cloudflare Tunnel's SSL handling contribute to redirect issues with Nextcloud?

Cloudflare Tunnel terminates SSL at Cloudflare's edge. By default, the connection from the Tunnel to your origin Nextcloud server might be HTTP. If Nextcloud isn't configured to trust the tunnel's proxy (via `trusted_proxies`) and doesn't know the original request was HTTPS, it might try to redirect the user to an HTTP version of the site, which Cloudflare then redirects back to HTTPS, causing the loop.