WIP; only advance order to delivery state

Use the hidden_field_tag rails helper and move it

app/controllers/split_checkout_controller.rb

@@ -1,3 +1,26 @@
 class SplitCheckoutController < CheckoutController
+  def update
+    byebug
+    params_adapter = Checkout::FormDataAdapter.new(permitted_params, @order, spree_current_user)
+    return action_failed unless @order.update(params_adapter.params[:order] || {})
 
+    checkout_workflow(params_adapter.shipping_method_id, params[:advance_to_state] || "delivery")
+  rescue Spree::Core::GatewayError => e
+    byebug
+    rescue_from_spree_gateway_error(e)
+  rescue StandardError => e
+    byebug
+    flash[:error] = I18n.t("checkout.failed")
+    action_failed(e)
+  ensure
+    @order.update_order!
+  end
+
+  private
+
+  def redirect_to_payment_gateway
+    return unless params&.dig(:order)&.dig(:payments_attributes)&.first&.dig(:payments_attributes)
+
+    super
+  end
 end