feat: use Rustls instead of native TLS for HTTPS requests

HTTPS requests are used to fetch
remote images in HTML emails,
to fetch autoconfig XML,
to POST requests for `DCACCOUNT:` QR codes
to make OAuth 2 API requests
and to connect to HTTPS proxies.

Rustls is more aggressive than OpenSSL
in deprecating cryptographic algorithms
so we cannot use it for IMAP and SMTP
to avoid breaking compatibility,
but for HTTPS requests listed
above this should not result in problems.

As HTTPS requests use only strict TLS checks,
there is no `strict_tls` argument
in `wrap_rustls` function.

Rustls is already used by iroh,
so this change does not introduce new dependencies.

src/net/tls.rs

@@ -1,4 +1,5 @@
 //! TLS support.
+use std::sync::Arc;
 
 use anyhow::Result;
 use async_native_tls::{Certificate, Protocol, TlsConnector, TlsStream};
@@ -46,7 +47,7 @@ pub async fn wrap_rustls<T: AsyncRead + AsyncWrite + Unpin>(
     let mut config = rustls::ClientConfig::builder()
         .with_root_certificates(root_cert_store)
         .with_no_client_auth();
-    config.alpn_protocols = alpn.into_iter().map(|s| s.as_bytes().to_vec()).collect();
+    config.alpn_protocols = alpn.iter().map(|s| s.as_bytes().to_vec()).collect();
 
     let tls = tokio_rustls::TlsConnector::from(Arc::new(config));
     let name = rustls_pki_types::ServerName::try_from(hostname)?.to_owned();