subscription_list [nfc]: Add a flag to hide channels where the user can't post

This will be used soon to avoid showing conversations from the
channel list where the current user can't post, specifically when
they don't have the permission.

Author: rajveermalviya

lib/widgets/subscription_list.dart

@@ -18,9 +18,11 @@ class SubscriptionListPageBody extends StatefulWidget {
   const SubscriptionListPageBody({
     super.key,
     this.showTopicListButtonInActionSheet = true,
+    this.hideChannelsIfUserCantPost = false,
   });
 
   final bool showTopicListButtonInActionSheet;
+  final bool hideChannelsIfUserCantPost;
 
   @override
   State<SubscriptionListPageBody> createState() => _SubscriptionListPageBodyState();
@@ -90,7 +92,14 @@ class _SubscriptionListPageBodyState extends State<SubscriptionListPageBody> wit
 
     final List<Subscription> pinned = [];
     final List<Subscription> unpinned = [];
+    final now = DateTime.now();
     for (final subscription in store.subscriptions.values) {
+      if (widget.hideChannelsIfUserCantPost) {
+        if (!store.hasPostingPermission(inChannel: subscription,
+              user: store.selfUser, byDate: now)) {
+          continue;
+        }
+      }
       if (subscription.pinToTop) {
         pinned.add(subscription);
       } else {