Transfer showLocalNotification, backgroundKeepAlive from LLC to Core

Signed-off-by: Sahil Kumar <[email protected]>

packages/flutter_widgets/lib/src/stream_chat.dart

@@ -34,11 +34,21 @@ class StreamChat extends StatefulWidget {
   final Widget child;
   final StreamChatThemeData streamChatThemeData;
 
+  /// The amount of time that will pass before disconnecting the client in the background
+  final Duration backgroundKeepAlive;
+
+  /// Handler called whenever the [client] receives a new [Event] while the app
+  /// is in background. Can be used to display various notifications depending
+  /// upon the [Event.type]
+  final EventHandler onBackgroundEventReceived;
+
   StreamChat({
     Key key,
     @required this.client,
     @required this.child,
     this.streamChatThemeData,
+    this.onBackgroundEventReceived,
+    this.backgroundKeepAlive = const Duration(minutes: 1),
   }) : super(
           key: key,
         );
@@ -82,8 +92,10 @@ class StreamChatState extends State<StreamChat> {
                 scaffoldBackgroundColor: streamTheme.colorTheme.white,
               ),
               child: StreamChatCore(
-                child: widget.child,
                 client: client,
+                child: widget.child,
+                onBackgroundEventReceived: widget.onBackgroundEventReceived,
+                backgroundKeepAlive: widget.backgroundKeepAlive,
               ),
             );
           },