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/amqp-order-handler.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+type AmqpOrderHandler struct {
+	Url        string
+	Connection *amqp.Connection
+	Channel    *amqp.Channel
+}
+
+func (h *AmqpOrderHandler) Connect() error {
+	conn, err := amqp.Dial(h.Url)
+	if err != nil {
+		return fmt.Errorf("failed to connect to RabbitMQ: %w", err)
+	}
+	h.Connection = conn
+
+	ch, err := conn.Channel()
+	if err != nil {
+		return fmt.Errorf("failed to open a channel: %w", err)
+	}
+	h.Channel = ch
+
+	return nil
+}
+
+func (h *AmqpOrderHandler) Close() error {
+	if h.Channel != nil {
+		h.Channel.Close()
+	}
+	if h.Connection != nil {
+		return h.Connection.Close()
+	}
+	return nil
+}
+
+func (h *AmqpOrderHandler) OrderCompleted(body []byte) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	err := h.Channel.PublishWithContext(ctx,
+		"orders", // exchange
+		"new",    // routing key
+		false,    // mandatory
+		false,    // immediate
+		amqp.Publishing{
+			ContentType: "application/json",
+			Body:        body,
+		})
+	if err != nil {
+		return fmt.Errorf("failed to publish a message: %w", err)
+	}
+
+	return nil
+}