tokio-xmpp: add option to split client

Adds an option to split the `tokio-xmpp::Client` into a Sender and
Receiver. To enable this, a client worker is added which drives the
stream in the background.

tokio-xmpp/src/client/receiver.rs

@@ -0,0 +1,48 @@
+// Copyright (c) 2025 xmpp-rs contributors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+use crate::Client;
+use crate::Event;
+use core::{pin::Pin, task::Context};
+use futures::StreamExt;
+use futures::{task::Poll, Stream};
+use std::sync::Arc;
+use tokio::sync::Mutex;
+use xmpp_parsers::{jid::Jid, stream_features::StreamFeatures};
+
+/// Read half of a [`Client`](crate::Client).
+#[derive(Debug)]
+pub struct ClientReceiver(pub(super) Arc<Mutex<Client>>);
+
+impl ClientReceiver {
+    /// Return the bound JID.
+    ///
+    /// See the documentation of [`Client::bound_jid`](crate::Client::bound_jid) for more
+    /// information.
+    pub async fn bound_jid(&self) -> Option<Jid> {
+        self.0.lock().await.bound_jid.clone()
+    }
+
+    /// Return the received stream features.
+    ///
+    /// See the documentation of [`Client::get_stream_features`](crate::Client::get_stream_features)
+    /// for more information.
+    pub async fn get_stream_features(&self) -> Option<StreamFeatures> {
+        self.0.lock().await.features.clone()
+    }
+}
+
+impl Stream for ClientReceiver {
+    type Item = Event;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
+        let Ok(mut client) = self.0.try_lock() else {
+            return Poll::Pending;
+        };
+
+        client.poll_next_unpin(cx)
+    }
+}