fix: remove old messaging documentation.

docs/06-concepts/15-streams.md

@@ -1,4 +1,4 @@
-# Streams and messaging
+# Streams
 
 For some applications, it's not enough to be able to call server-side methods. You may also want to push data from the server to the client or send data two-way. Examples include real-time games or chat applications. Luckily, Serverpod supports a framework for streaming data. It's possible to stream any serialized objects to or from any endpoint.
 
@@ -144,43 +144,6 @@ Future<void> streamOpened(StreamingSession session) async {
 
 You can access the user object at any time by calling the `getUserObject` method. The user object is automatically discarded when a session ends.
 
-#### Internal server messaging
-
-A typical scenario when working with streams is to pass on messages from one user to another. For instance, if one client sends a chat message to the server, the server should send it to the correct user. Serverpod comes with a built-in messaging system that makes this easy. You can pass messages locally on a single server, but messages are passed through Redis by default. Passing the messages through Redis makes it possible to send the messages between multiple servers in a cluster.
-
-In most cases, it's easiest to subscribe to a message channel in the `streamOpened` method. The subscription will automatically be disposed of when the stream is closed. The following example will forward any message sent to a user identified by its user id.
-
-```dart
-@override
-Future<void> streamOpened(StreamingSession session) async {
-  final authenticationInfo = await session.authenticated;
-  final userId = authenticationInfo?.userId;
-  session.messages.addListener(
-    'user_$userId',
-    (message) {
-      sendStreamMessage(session, message);
-    },
-  );
-}
-```
-
-In your `handleStreamMessage` method, you can pass on messages to the correct channel.
-
-```dart
-@override
-Future<void> handleStreamMessage(
-  StreamingSession session,
-  SerializableModel message,
-) async {
-  if (message is MyChatMessage) {
-    session.messages.postMessage(
-      'user_${message.recipientId}',
-      message,
-    );
-  }
-}
-```
-
 ### Handling streams in your app
 
 Before you can access streams in your client, you need to connect to the server's web socket. You do this by calling connectWebSocket on your client.