Implement CallKit "setMuted" callback (#197)

* Add missing CallKit callback of muting

* Remove unnecessary call state checking

Author: bobiechen-twilio

ObjcVoiceQuickstart/ViewController.m

@@ -600,14 +600,24 @@ - (void)provider:(CXProvider *)provider performEndCallAction:(CXEndCallAction *)
 
 - (void)provider:(CXProvider *)provider performSetHeldCallAction:(CXSetHeldCallAction *)action {
     TVOCall *call = self.activeCalls[action.callUUID.UUIDString];
-    if (call && call.state == TVOCallStateConnected) {
+    if (call) {
         [call setOnHold:action.isOnHold];
         [action fulfill];
     } else {
         [action fail];
     }
 }
 
+- (void)provider:(CXProvider *)provider performSetMutedCallAction:(CXSetMutedCallAction *)action {
+    TVOCall *call = self.activeCalls[action.callUUID.UUIDString];
+    if (call) {
+        [call setMuted:action.isMuted];
+        [action fulfill];
+    } else {
+        [action fail];
+    }
+}
+
 #pragma mark - CallKit Actions
 - (void)performStartCallActionWithUUID:(NSUUID *)uuid handle:(NSString *)handle {
     if (uuid == nil || handle == nil) {