FIX: Site setting changes for boolean should be logged as true/false (#16888)

Previously true/false sometimes was logged as t or f

app/services/staff_action_logger.rb

@@ -182,8 +182,8 @@ class StaffActionLogger
     UserHistory.create!(params(opts).merge(
       action: UserHistory.actions[:change_site_setting],
       subject: setting_name,
-      previous_value: previous_value,
-      new_value: new_value
+      previous_value: previous_value&.to_s,
+      new_value: new_value&.to_s
     ))
   end
 

spec/services/staff_action_logger_spec.rb

@@ -145,6 +145,18 @@ describe StaffActionLogger do
     it "creates a new UserHistory record" do
       expect { logger.log_site_setting_change('title', 'Discourse', 'My Site') }.to change { UserHistory.count }.by(1)
     end
+
+    it "logs boolean values" do
+      log_record = logger.log_site_setting_change("allow_user_locale", true, false)
+      expect(log_record.previous_value).to eq("true")
+      expect(log_record.new_value).to eq("false")
+    end
+
+    it "logs nil values" do
+      log_record = logger.log_site_setting_change("title", nil, nil)
+      expect(log_record.previous_value).to be_nil
+      expect(log_record.new_value).to be_nil
+    end
   end
 
   describe "log_theme_change" do