Subscription permission API (#68)

* signal

* request

* implement

* rename event

* ref

* adjustments based on review

* override subscribed

* move events emit

* fix subscription state

* minor change

* update example for permissions demo

* format & subscriptionState as computed property

* prepare macos build

* unsubscribed event when subscription not allowed

example/lib/widgets/controls.dart

@@ -136,6 +136,19 @@ class _ControlsWidgetState extends State<ControlsWidget> {
     }
   }
 
+  void _onTapUpdateSubscribePermission() async {
+    final result = await context.showSubscribePermissionDialog();
+    if (result != null) {
+      try {
+        widget.room.localParticipant?.setTrackSubscriptionPermissions(
+          allParticipantsAllowed: result,
+        );
+      } catch (error) {
+        await context.showErrorDialog(error);
+      }
+    }
+  }
+
   void _onTapSendData() async {
     final result = await context.showSendDataDialog();
     if (result == true) {
@@ -220,6 +233,11 @@ class _ControlsWidgetState extends State<ControlsWidget> {
             icon: const Icon(EvaIcons.refresh),
             tooltip: 're-connect',
           ),
+          IconButton(
+            onPressed: _onTapUpdateSubscribePermission,
+            icon: const Icon(EvaIcons.settings2),
+            tooltip: 'Subscribe permission',
+          ),
         ],
       ),
     );