Offer {Resource,Node,Domain}Ref on Jid API

This provides a non-copying API, which is generally favourable. The
other accessors were removed, because the intent was to provide this
"most sensible" API via the "default" (i.e. shortest, most concisely
named) functions.

tokio-xmpp/src/client/bind.rs

@@ -15,8 +15,8 @@ pub async fn bind<S: AsyncRead + AsyncWrite + Unpin>(
     if stream.stream_features.can_bind() {
         let resource = stream
             .jid
-            .resource_str()
-            .and_then(|resource| Some(resource.to_owned()));
+            .resource()
+            .and_then(|resource| Some(resource.to_string()));
         let iq = Iq::from_set(BIND_REQ_ID, BindQuery::new(resource));
         stream.send_stanza(iq).await?;
 

tokio-xmpp/src/client/connect.rs

@@ -13,7 +13,7 @@ pub async fn client_login<C: ServerConnector>(
     jid: Jid,
     password: String,
 ) -> Result<XMPPStream<C::Stream>, Error> {
-    let username = jid.node_str().unwrap();
+    let username = jid.node().unwrap().as_str();
     let password = password;
 
     let xmpp_stream = server.connect(&jid, ns::JABBER_CLIENT).await?;