add template variables

app/controllers/api/submissions_controller.rb

@@ -184,6 +184,7 @@ module Api
         :send_email, :send_sms, :bcc_completed, :completed_redirect_url, :reply_to, :go_to_last,
         :require_phone_2fa, :expire_at, :name,
         {
+          variables: {},
           message: %i[subject body],
           submitters: [[:send_email, :send_sms, :completed_redirect_url, :uuid, :name, :email, :role,
                         :completed, :phone, :application_key, :external_id, :reply_to, :go_to_last,