Check if external signaling server has a MCU.

Signed-off-by: Ivan Sein <ivan@nextcloud.com>

VideoCalls/NCCallController.m

@@ -98,7 +98,9 @@ static NSString * const kNCVideoTrackKind = @"video";
             [self startMonitoringMicrophoneAudioLevel];
             if ([[NCExternalSignalingController sharedInstance] isEnabled]) {
                 _userSessionId = [[NCExternalSignalingController sharedInstance] sessionId];
-                [self createOwnPublishPeerConnection];
+                if ([[NCExternalSignalingController sharedInstance] hasMCU]) {
+                    [self createOwnPublishPeerConnection];
+                }
             } else {
                 [_signalingController startPullingSignalingMessages];
             }
@@ -336,7 +338,7 @@ static NSString * const kNCVideoTrackKind = @"video";
         peerConnectionWrapper = [[NCPeerConnection alloc] initWithSessionId:sessionId andICEServers:iceServers forAudioOnlyCall:_isAudioOnly];
         peerConnectionWrapper.delegate = self;
         // TODO: Try to get display name here
-        if (![[NCExternalSignalingController sharedInstance] isEnabled]) {
+        if (![[NCExternalSignalingController sharedInstance] hasMCU]) {
             [peerConnectionWrapper.peerConnection addStream:_localStream];
         }
         
@@ -469,7 +471,7 @@ static NSString * const kNCVideoTrackKind = @"video";
     
     for (NSString *sessionId in newSessions) {
         if (![_connectionsDict objectForKey:sessionId]) {
-            if ([[NCExternalSignalingController sharedInstance] isEnabled]) {
+            if ([[NCExternalSignalingController sharedInstance] hasMCU]) {
                 NSLog(@"Requesting offer to the MCU");
                 [[NCExternalSignalingController sharedInstance] requestOfferForSessionId:sessionId andRoomType:@"video"];
             } else {

VideoCalls/NCExternalSignalingController.h

@@ -17,6 +17,7 @@ extern NSString * const NCESReceivedParticipantListMessageNotification;
 
 + (instancetype)sharedInstance;
 - (BOOL)isEnabled;
+- (BOOL)hasMCU;
 - (NSString *)sessionId;
 - (void)setServer:(NSString *)serverUrl andTicket:(NSString *)ticket;
 - (void)joinRoom:(NSString *)roomId withSessionId:(NSString *)sessionId;

VideoCalls/NCExternalSignalingController.m

@@ -50,6 +50,11 @@ NSString * const NCESReceivedParticipantListMessageNotification = @"NCESReceived
     return (_serverUrl) ? YES : NO;
 }
 
+- (BOOL)hasMCU
+{
+    return _mcuSupport;
+}
+
 - (NSString *)sessionId
 {
     return _sessionId;
@@ -173,7 +178,12 @@ NSString * const NCESReceivedParticipantListMessageNotification = @"NCESReceived
 - (void)helloResponseReceived:(NSDictionary *)helloDict
 {
     _resumeId = [helloDict objectForKey:@"resumeid"];
-    // Get server features
+    NSArray *serverFeatures = [[helloDict objectForKey:@"server"] objectForKey:@"features"];
+    for (NSString *feature in serverFeatures) {
+        if ([feature isEqualToString:@"mcu"]) {
+            _mcuSupport = YES;
+        }
+    }
 }
 
 - (void)errorResponseReceived:(NSDictionary *)errorDict