Add record to track overridden limits

Before, we were relying on just changing the cards_count in account, but this
could create problems where the system to calculate the next card number fails due
to the unique constraint.

saas/app/controllers/admin/overridden_limits_controller.rb

@@ -0,0 +1,8 @@
+class Admin::OverriddenLimitsController < AdminController
+  include Admin::AccountScoped
+
+  def destroy
+    @account.reset_overridden_limits
+    redirect_to saas.edit_admin_account_path(@account.external_account_id), notice: "Limits reset"
+  end
+end