model test [nfc]: Rename stream to channel

Fixes parts of #631

Author: Khader-1

test/api/model/model_test.dart

@@ -118,19 +118,19 @@ void main() {
   });
 
   group('Message', () {
-    Map<String, dynamic> baseStreamJson() =>
+    Map<String, dynamic> baseChannelJson() =>
       deepToJson(eg.channelMessage()) as Map<String, dynamic>;
 
     test('subject -> topic', () {
-      check(baseStreamJson()).not((it) => it.containsKey('topic'));
-      check(Message.fromJson(baseStreamJson()
+      check(baseChannelJson()).not((it) => it.containsKey('topic'));
+      check(Message.fromJson(baseChannelJson()
         ..['subject'] = 'hello'
       )).topic.equals('hello');
     });
 
     test('match_subject -> matchTopic', () {
-      check(baseStreamJson()).not((it) => it.containsKey('match_topic'));
-      check(Message.fromJson(baseStreamJson()
+      check(baseChannelJson()).not((it) => it.containsKey('match_topic'));
+      check(Message.fromJson(baseChannelJson()
         ..['match_subject'] = 'yo'
       )).matchTopic.equals('yo');
     });