Refactor to make it more like the Android app

web/src/app/Subscription.js

@@ -6,24 +6,35 @@ export default class Subscription {
     topic = '';
     notifications = [];
     lastActive = null;
+
     constructor(baseUrl, topic) {
         this.id = topicUrl(baseUrl, topic);
         this.baseUrl = baseUrl;
         this.topic = topic;
     }
+
     addNotification(notification) {
         if (notification.time === null) {
-            return;
+            return this;
         }
         this.notifications.push(notification);
         this.lastActive = notification.time;
+        return this;
     }
+
+    addNotifications(notifications) {
+        notifications.forEach(n => this.addNotification(n));
+        return this;
+    }
+
     url() {
         return this.id;
     }
+
     wsUrl() {
         return topicUrlWs(this.baseUrl, this.topic);
     }
+
     shortUrl() {
         return shortTopicUrl(this.baseUrl, this.topic);
     }