FIX: Do not return muted child categories termless hashtag search (#19526)

We generally do not return muted child categories to the user
if they have muted the parent category, this commit respects that
rule for CategoryHashtagDataSource

app/services/category_hashtag_data_source.rb

@@ -74,13 +74,13 @@ class CategoryHashtagDataSource
     Category
       .includes(:parent_category)
       .secured(guardian)
-      .joins(
-        "LEFT JOIN category_users ON category_users.user_id = #{guardian.user.id}
-        AND category_users.category_id = categories.id",
-      )
       .where(
-        "category_users.notification_level IS NULL OR category_users.notification_level != ?",
-        CategoryUser.notification_levels[:muted],
+        "categories.id NOT IN (#{
+          CategoryUser
+            .muted_category_ids_query(guardian.user, include_direct: true)
+            .select("categories.id")
+            .to_sql
+        })",
       )
       .order(topic_count: :desc)
       .take(limit)

spec/services/category_hashtag_data_source_spec.rb

@@ -91,6 +91,15 @@ RSpec.describe CategoryHashtagDataSource do
       )
       expect(described_class.search_without_term(guardian, 5).map(&:slug)).not_to include("random")
     end
+
+    it "does not return child categories where the user has muted the parent" do
+      CategoryUser.create!(
+        user: user,
+        category: parent_category,
+        notification_level: CategoryUser.notification_levels[:muted],
+      )
+      expect(described_class.search_without_term(guardian, 5).map(&:slug)).not_to include("random")
+    end
   end
 
   describe "#search_sort" do