Implement proper handling for inactive/active subscriptions

flutter/lib/models/subscription.dart

@@ -6,6 +6,7 @@ class Subscription {
   final String channelInternalName;
   final String timestampCreated;
   final bool confirmed;
+  final bool active;
 
   const Subscription({
     required this.subscriptionID,
@@ -15,6 +16,7 @@ class Subscription {
     required this.channelInternalName,
     required this.timestampCreated,
     required this.confirmed,
+    required this.active,
   });
 
   factory Subscription.fromJson(Map<String, dynamic> json) {
@@ -26,6 +28,7 @@ class Subscription {
       channelInternalName: json['channel_internal_name'] as String,
       timestampCreated: json['timestamp_created'] as String,
       confirmed: json['confirmed'] as bool,
+      active: json['active'] as bool,
     );
   }