feat(order): 重构退款全流程并新增申请退款中状态

- 订单状态新增「6 申请退款中」，用户申请退款原子流转并落待审核退款流水
- 退款失败回退订单至已支付并恢复被取消的权益发放任务
- 新增虚拟支付退款查单兜底任务，反查超时订单并自动订正
- 会员包来源额度不叠加，扣减/回退/回收口径统一为只取生效一份
- 退款回收流水按吊销前后有效剩余差值记账，避免无效回收记录
- 同步更新 README 与 Stitch 设计文档

internal/service/refund_apply_test.go

@@ -0,0 +1,96 @@
+package service
+
+import (
+	"context"
+	"testing"
+
+	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/internal/dto"
+	"git.lzcwy.cn/zhengchiliu/zt-closet-backend/pkg/errcode"
+	"github.com/DATA-DOG/go-sqlmock"
+)
+
+// TestRefundApplyMarksOrderRefunding 申请退款受理成功：返回待处理退款流水信息，订单 2 -> 6 由 DAO 事务内完成。
+func TestRefundApplyMarksOrderRefunding(t *testing.T) {
+	mock := setupOrderQuotaTest(t)
+	mock.ExpectQuery("SELECT .* FROM `orders` WHERE order_no = \\?").
+		WillReturnRows(sqlmock.NewRows([]string{"id", "order_no", "user_id", "order_status", "pay_amount", "pay_channel"}).
+			AddRow(8, "ORDER-1", 7, 2, 990, 1))
+	mock.ExpectBegin()
+	mock.ExpectQuery("SELECT .* FROM `orders` .*FOR UPDATE").
+		WillReturnRows(sqlmock.NewRows([]string{"id", "order_no", "user_id", "order_status", "pay_amount"}).
+			AddRow(8, "ORDER-1", 7, 2, 990))
+	mock.ExpectQuery("SELECT .* FROM `refund_flow_logs`").
+		WillReturnRows(sqlmock.NewRows([]string{"id"}))
+	mock.ExpectExec("INSERT INTO `refund_flow_logs`").WillReturnResult(sqlmock.NewResult(1, 1))
+	mock.ExpectExec("UPDATE `orders` SET").WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectCommit()
+
+	resp, e := NewOrderService().RefundApply(context.Background(), 7,
+		&dto.RefundApplyRequest{OrderNo: "ORDER-1", Reason: "不想要了"})
+	if e != nil {
+		t.Fatalf("unexpected error: %v", e)
+	}
+	if resp == nil || resp.RefundAmount != 990 || resp.Status != RefundStatusPending || resp.RefundNo == "" {
+		t.Fatalf("unexpected response: %+v", resp)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestRefundApplyRejectsRepeatApply 重复/并发申请被 DAO 拒绝时映射为「当前状态不允许退款」。
+func TestRefundApplyRejectsRepeatApply(t *testing.T) {
+	mock := setupOrderQuotaTest(t)
+	mock.ExpectQuery("SELECT .* FROM `orders` WHERE order_no = \\?").
+		WillReturnRows(sqlmock.NewRows([]string{"id", "order_no", "user_id", "order_status", "pay_amount", "pay_channel"}).
+			AddRow(8, "ORDER-1", 7, 2, 990, 1))
+	// 行锁内读到订单已被并发请求置为 6 申请退款中：拒绝且不产生任何写入。
+	mock.ExpectBegin()
+	mock.ExpectQuery("SELECT .* FROM `orders` .*FOR UPDATE").
+		WillReturnRows(sqlmock.NewRows([]string{"id", "order_no", "user_id", "order_status"}).
+			AddRow(8, "ORDER-1", 7, OrderStatusRefunding))
+	mock.ExpectCommit()
+
+	resp, e := NewOrderService().RefundApply(context.Background(), 7,
+		&dto.RefundApplyRequest{OrderNo: "ORDER-1", Reason: "重复申请"})
+	if resp != nil || e != errcode.RefundNotAllowed {
+		t.Fatalf("resp=%v err=%v, want RefundNotAllowed", resp, e)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestRefundApplyRejectsIOSVirtualOrder iOS 虚拟支付订单不走本接口，引导用户走 App Store。
+func TestRefundApplyRejectsIOSVirtualOrder(t *testing.T) {
+	mock := setupOrderQuotaTest(t)
+	mock.ExpectQuery("SELECT .* FROM `orders` WHERE order_no = \\?").
+		WillReturnRows(sqlmock.NewRows([]string{"id", "order_no", "user_id", "order_status", "pay_amount", "pay_channel", "xpay_platform"}).
+			AddRow(8, "ORDER-1", 7, 2, 990, 2, "ios"))
+
+	resp, e := NewOrderService().RefundApply(context.Background(), 7,
+		&dto.RefundApplyRequest{OrderNo: "ORDER-1", Reason: "不想要了"})
+	if resp != nil || e != errcode.IOSRefundViaAppStore {
+		t.Fatalf("resp=%v err=%v, want IOSRefundViaAppStore", resp, e)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TestRefundApplyRejectsOtherUserOrder 非本人订单不允许申请退款（归属校验先于状态校验）。
+func TestRefundApplyRejectsOtherUserOrder(t *testing.T) {
+	mock := setupOrderQuotaTest(t)
+	mock.ExpectQuery("SELECT .* FROM `orders` WHERE order_no = \\?").
+		WillReturnRows(sqlmock.NewRows([]string{"id", "order_no", "user_id", "order_status", "pay_amount", "pay_channel"}).
+			AddRow(8, "ORDER-1", 9, 2, 990, 1))
+
+	resp, e := NewOrderService().RefundApply(context.Background(), 7,
+		&dto.RefundApplyRequest{OrderNo: "ORDER-1", Reason: "越权申请"})
+	if resp != nil || e != errcode.Forbidden {
+		t.Fatalf("resp=%v err=%v, want Forbidden", resp, e)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatal(err)
+	}
+}