recent dms [nfc]: Add a flag to hide DMs where user can't post

This will be used soon to avoid showing conversations from the
recent DMs list where the current user can't post, specifically
when a conversation has one or more deactivated user.

Author: rajveermalviya

lib/widgets/recent_dm_conversations.dart

@@ -15,7 +15,12 @@ import 'unread_count_badge.dart';
 import 'user.dart';
 
 class RecentDmConversationsPageBody extends StatefulWidget {
-  const RecentDmConversationsPageBody({super.key});
+  const RecentDmConversationsPageBody({
+    super.key,
+    this.hideDmsIfUserCantPost = false,
+  });
+
+  final bool hideDmsIfUserCantPost;
 
   @override
   State<RecentDmConversationsPageBody> createState() => _RecentDmConversationsPageBodyState();
@@ -76,6 +81,15 @@ class _RecentDmConversationsPageBodyState extends State<RecentDmConversationsPag
                   //   for these conversations we're filtering out?
                   return SizedBox.shrink();
                 }
+                if (widget.hideDmsIfUserCantPost) {
+                  // TODO(#791) handle other cases where user can't post
+                  final hasDeactivatedUser =
+                    narrow.otherRecipientIds.any(
+                      (id) => !(store.getUser(id)?.isActive ?? true));
+                  if (hasDeactivatedUser) {
+                    return SizedBox.shrink();
+                  }
+                }
                 return RecentDmConversationsItem(
                   narrow: narrow,
                   unreadCount: unreadsModel!.countInDmNarrow(narrow));