DEV: Make more group-based settings client: false (#25735)

Affects the following settings:

delete_all_posts_and_topics_allowed_groups
experimental_new_new_view_groups
enable_experimental_admin_ui_groups
custom_summarization_allowed_groups
pm_tags_allowed_for_groups
chat_allowed_groups
direct_message_enabled_groups
chat_message_flag_allowed_groups

This turns off client: true for these group-based settings,
because there is no guarantee that the current user gets all
their group memberships serialized to the client. Better to check
server-side first.

plugins/chat/plugin.rb

@@ -143,6 +143,15 @@ after_initialize do
     end,
   ) { true }
 
+  add_to_serializer(
+    :current_user,
+    :can_direct_message,
+    include_condition: -> do
+      return @can_direct_message if defined?(@can_direct_message)
+      @can_direct_message = SiteSetting.chat_enabled && scope.can_direct_message?
+    end,
+  ) { true }
+
   add_to_serializer(
     :current_user,
     :has_chat_enabled,