SECURITY: Restrict display of topic titles associated with user badges (#18768)

Before this commit, we did not have guardian checks in place to determine if a
topic's title associated with a user badge should be displayed or not.
This means that the topic title of topics with restricted access
could be leaked to anon and users without access if certain conditions
are met. While we will not specify the conditions required, we have internally
assessed that the odds of meeting such conditions are low.

With this commit, we will now apply a guardian check to ensure that the
current user is able to see a topic before the topic's title is included
in the serialized object of a `UserBadge`.

app/controllers/user_badges_controller.rb

@@ -24,11 +24,19 @@ class UserBadgesController < ApplicationController
       user_badges = user_badges.offset(offset.to_i)
     end
 
+    user_badges_topic_ids = user_badges.map { |user_badge| user_badge.post&.topic_id }.compact
+
     user_badges = UserBadges.new(user_badges: user_badges,
                                  username: params[:username],
                                  grant_count: grant_count)
 
-    render_serialized(user_badges, UserBadgesSerializer, root: :user_badge_info, include_long_description: true)
+    render_serialized(
+      user_badges,
+      UserBadgesSerializer,
+      root: :user_badge_info,
+      include_long_description: true,
+      allowed_user_badge_topic_ids: guardian.can_see_topic_ids(topic_ids: user_badges_topic_ids)
+    )
   end
 
   def username
@@ -46,9 +54,12 @@ class UserBadgesController < ApplicationController
       .includes(post: :topic)
       .includes(:granted_by)
 
+    user_badges_topic_ids = user_badges.map { |user_badge| user_badge.post&.topic_id }.compact
+
     render_serialized(
       user_badges,
       DetailedUserBadgeSerializer,
+      allowed_user_badge_topic_ids: guardian.can_see_topic_ids(topic_ids: user_badges_topic_ids),
       root: :user_badges,
     )
   end