try new errors

cmd/cart/mutation_add_voucher.go

@@ -4,24 +4,37 @@ import (
 	"fmt"
 	"slices"
 
+	"git.tornberg.me/go-cart-actor/pkg/actor"
 	"git.tornberg.me/go-cart-actor/pkg/messages"
 	"git.tornberg.me/go-cart-actor/pkg/voucher"
 )
 
 func (ctx *MutationContext) AddVoucher(g *CartGrain, m *messages.AddVoucher) error {
 	if m == nil {
-		return fmt.Errorf("AddVoucher: nil payload")
+		return &actor.MutationError{
+			Message:    "AddVoucher: nil payload",
+			Code:       1001,
+			StatusCode: 400,
+		}
 	}
 
 	if slices.ContainsFunc(g.Vouchers, func(v *voucher.Voucher) bool {
 		return v.Code == m.Code
 	}) {
-		return fmt.Errorf("voucher already applied")
+		return &actor.MutationError{
+			Message:    "voucher already applied",
+			Code:       1002,
+			StatusCode: 400,
+		}
 	}
 
 	voucherData, err := ctx.VoucherService.GetVoucher(m.Code)
 	if err != nil {
-		return fmt.Errorf("cant find voucher: %w", err)
+		return &actor.MutationError{
+			Message:    fmt.Sprintf("cant find voucher: %v", err),
+			Code:       1003,
+			StatusCode: 400,
+		}
 	}
 
 	if voucherData == nil {