Implement proper handling for inactive/active subscriptions

flutter/lib/api/api_client.dart

@@ -524,6 +524,32 @@ class APIClient {
     );
   }
 
+  static Future<Subscription> activateSubscription(TokenSource auth, String channelID, String subID) async {
+    return await _request(
+      name: 'activateSubscription',
+      method: 'PATCH',
+      relURL: 'users/${auth.getUserID()}/subscriptions/${subID}',
+      jsonBody: {
+        'active': true,
+      },
+      fn: Subscription.fromJson,
+      authToken: auth.getToken(),
+    );
+  }
+
+  static Future<Subscription> deactivateSubscription(TokenSource auth, String channelID, String subID) async {
+    return await _request(
+      name: 'deactivateSubscription',
+      method: 'PATCH',
+      relURL: 'users/${auth.getUserID()}/subscriptions/${subID}',
+      jsonBody: {
+        'active': false,
+      },
+      fn: Subscription.fromJson,
+      authToken: auth.getToken(),
+    );
+  }
+
   static Future<SendMessageResponse> sendMessage(String userid, String keytoken, String text, {String? channel, String? content, String? messageID, int? priority, String? senderName, DateTime? timestamp}) async {
     return await _request(
       name: 'sendMessage',