Complete refactor to new grpc control plane and only http proxy for carts (#4)

Co-authored-by: matst80 <mats.tornberg@gmail.com>
Reviewed-on: https://git.tornberg.me/mats/go-cart-actor/pulls/4
Co-authored-by: Mats Törnberg <mats@tornberg.me>
Co-committed-by: Mats Törnberg <mats@tornberg.me>

cmd/cart/cart_grain_totals_test.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"testing"
+)
+
+// helper to create a cart grain with items and deliveries
+func newTestCart() *CartGrain {
+	return &CartGrain{Items: []*CartItem{}, Deliveries: []*CartDelivery{}, Vouchers: []*Voucher{}, Notifications: []CartNotification{}}
+}
+
+func TestCartGrainUpdateTotalsBasic(t *testing.T) {
+	c := newTestCart()
+	// Item1 price 1250 (ex 1000 vat 250) org price higher -> discount 200 per unit
+	item1Price := Price{IncVat: 1250, VatRates: map[float32]int64{25: 250}}
+	item1Org := &Price{IncVat: 1500, VatRates: map[float32]int64{25: 300}}
+	item2Price := Price{IncVat: 2000, VatRates: map[float32]int64{25: 400}}
+	c.Items = []*CartItem{
+		{Id: 1, Price: item1Price, OrgPrice: item1Org, Quantity: 2},
+		{Id: 2, Price: item2Price, OrgPrice: &item2Price, Quantity: 1},
+	}
+	deliveryPrice := Price{IncVat: 4900, VatRates: map[float32]int64{25: 980}}
+	c.Deliveries = []*CartDelivery{{Id: 1, Price: deliveryPrice, Items: []uint32{1, 2}}}
+
+	c.UpdateTotals()
+
+	// Expected totals: sum inc vat of items * qty plus delivery
+	// item1 total inc = 1250*2 = 2500
+	// item2 total inc = 2000*1 = 2000
+	// delivery inc = 4900
+	expectedInc := int64(2500 + 2000 + 4900)
+	if c.TotalPrice.IncVat != expectedInc {
+		t.Fatalf("TotalPrice IncVat expected %d got %d", expectedInc, c.TotalPrice.IncVat)
+	}
+
+	// Discount: current implementation computes (OrgPrice - Price) ignoring quantity -> 1500-1250=250
+	if c.TotalDiscount.IncVat != 250 {
+		t.Fatalf("TotalDiscount expected 250 got %d", c.TotalDiscount.IncVat)
+	}
+}
+
+func TestCartGrainUpdateTotalsNoItems(t *testing.T) {
+	c := newTestCart()
+	c.UpdateTotals()
+	if c.TotalPrice.IncVat != 0 || c.TotalDiscount.IncVat != 0 {
+		t.Fatalf("expected zero totals got %+v", c)
+	}
+}