Revert "PERF: Cache categories in Site model."

This reverts commit 7dc0f88acd.

app/models/site.rb

@@ -28,42 +28,16 @@ class Site
     UserField.order(:position).all
   end
 
-  CATEGORIES_CACHE_KEY = "site_categories"
-
-  def self.clear_cache
-    Discourse.cache.delete(CATEGORIES_CACHE_KEY)
-  end
-
-  def self.all_categories_cache
-    # Categories do not change often so there is no need for us to run the
-    # same query and spend time creating ActiveRecord objects for every requests.
-    #
-    # Do note that any new association added to the eager loading needs a
-    # corresponding ActiveRecord callback to clear the categories cache.
-    Discourse.cache.fetch(CATEGORIES_CACHE_KEY, expires_in: 30.minutes) do
+  def categories
+    @categories ||= begin
       categories = Category
-        .includes(:uploaded_logo, :uploaded_background, :tags, :tag_groups, :required_tag_group)
+        .includes(:uploaded_logo, :uploaded_background, :tags, :tag_groups)
+        .secured(@guardian)
         .joins('LEFT JOIN topics t on t.id = categories.topic_id')
         .select('categories.*, t.slug topic_slug')
         .order(:position)
-        .to_a
 
-      ActiveModel::ArraySerializer.new(
-        categories,
-        each_serializer: SiteCategorySerializer
-      ).as_json
-    end
-  end
-
-  def categories
-    @categories ||= begin
-      categories = []
-
-      self.class.all_categories_cache.each do |category|
-        if @guardian.can_see_serialized_category?(category_id: category["id"], read_restricted: category["read_restricted"])
-          categories << OpenStruct.new(category)
-        end
-      end
+      categories = categories.to_a
 
       with_children = Set.new
       categories.each do |c|