store [nfc]: Rename _streams to _channels

Fixes parts of #631

Author: Khader-1

lib/model/store.dart

@@ -274,7 +274,7 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
        assert(realmUrl == globalStore.getAccount(accountId)!.realmUrl),
        assert(realmUrl == connection.realmUrl),
        _globalStore = globalStore,
-       _streams = channels,
+       _channels = channels,
        _messages = messages;
 
   ////////////////////////////////////////////////////////////////
@@ -320,22 +320,22 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
   final Map<int, User> users;
 
   ////////////////////////////////
-  // Streams, topics, and stuff about them.
+  // Channels, topics, and stuff about them.
 
   @override
-  Map<int, Channel> get channels => _streams.channels;
+  Map<int, Channel> get channels => _channels.channels;
   @override
-  Map<String, Channel> get channelsByName => _streams.channelsByName;
+  Map<String, Channel> get channelsByName => _channels.channelsByName;
   @override
-  Map<int, Subscription> get subscriptions => _streams.subscriptions;
+  Map<int, Subscription> get subscriptions => _channels.subscriptions;
   @override
   UserTopicVisibilityPolicy topicVisibilityPolicy(int channelId, String topic) =>
-    _streams.topicVisibilityPolicy(channelId, topic);
+    _channels.topicVisibilityPolicy(channelId, topic);
 
-  final ChannelStoreImpl _streams;
+  final ChannelStoreImpl _channels;
 
   @visibleForTesting
-  ChannelStoreImpl get debugStreamStore => _streams;
+  ChannelStoreImpl get debugStreamStore => _channels;
 
   ////////////////////////////////
   // Messages, and summaries of messages.
@@ -456,15 +456,15 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
       notifyListeners();
     } else if (event is StreamEvent) {
       assert(debugLog("server event: stream/${event.op}"));
-      _streams.handleChannelEvent(event);
+      _channels.handleChannelEvent(event);
       notifyListeners();
     } else if (event is SubscriptionEvent) {
       assert(debugLog("server event: subscription/${event.op}"));
-      _streams.handleSubscriptionEvent(event);
+      _channels.handleSubscriptionEvent(event);
       notifyListeners();
     } else if (event is UserTopicEvent) {
       assert(debugLog("server event: user_topic"));
-      _streams.handleUserTopicEvent(event);
+      _channels.handleUserTopicEvent(event);
       notifyListeners();
     } else if (event is MessageEvent) {
       assert(debugLog("server event: message ${jsonEncode(event.message.toJson())}"));