Re-add invoice settings controller removed by mistake

app/controllers/admin/invoice_settings_controller.rb

@@ -0,0 +1,13 @@
+module Admin
+  class InvoiceSettingsController < Spree::Admin::BaseController
+    def update
+      Spree::Config.set(params[:preferences])
+
+      respond_to do |format|
+        format.html {
+          redirect_to main_app.edit_admin_invoice_settings_path
+        }
+      end
+    end
+  end
+end