feat: add test database setup and usage helpers

- Introduced a new test file for setting up an in-memory SQLite database for testing purposes.
- Added helper functions for seeding test data, including users, plans, subscriptions, and wallet transactions.
- Implemented usage helpers to load user video counts and storage usage.
- Created user payload struct and functions to build user payloads with preferences and wallet balance.
- Refactored gRPC server setup to include new services and handlers.
- Updated proto files to simplify service definitions by removing redundant service prefixes.

internal/transport/mqtt/client.go

@@ -0,0 +1,86 @@
+package mqtt
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	mqtt "github.com/eclipse/paho.mqtt.golang"
+)
+
+type Client interface {
+	Publish(ctx context.Context, topic string, payload []byte) error
+	Subscribe(topic string, handler MessageHandler) error
+	Disconnect()
+}
+
+type MessageHandler func(topic string, payload []byte)
+
+type client struct {
+	cli mqtt.Client
+}
+
+func NewClient(broker string, clientID string) (Client, error) {
+	opts := mqtt.NewClientOptions().
+		AddBroker(broker).
+		SetClientID(clientID).
+		SetAutoReconnect(true).
+		SetConnectRetry(true).
+		SetConnectRetryInterval(3 * time.Second)
+
+	opts.OnConnect = func(c mqtt.Client) {
+		fmt.Println("MQTT connected")
+	}
+
+	opts.OnConnectionLost = func(c mqtt.Client, err error) {
+		fmt.Println("MQTT connection lost:", err)
+	}
+
+	c := mqtt.NewClient(opts)
+
+	token := c.Connect()
+	if ok := token.WaitTimeout(5 * time.Second); !ok {
+		return nil, fmt.Errorf("mqtt connect timeout")
+	}
+	if err := token.Error(); err != nil {
+		return nil, err
+	}
+
+	return &client{cli: c}, nil
+}
+
+func (c *client) Publish(ctx context.Context, topic string, payload []byte) error {
+	token := c.cli.Publish(topic, 1, false, payload)
+
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	case <-waitToken(token):
+		return token.Error()
+	}
+}
+
+func waitToken(t mqtt.Token) <-chan struct{} {
+	ch := make(chan struct{})
+	go func() {
+		t.Wait()
+		close(ch)
+	}()
+	return ch
+}
+
+func (c *client) Subscribe(topic string, handler MessageHandler) error {
+	token := c.cli.Subscribe(topic, 1, func(client mqtt.Client, msg mqtt.Message) {
+		handler(msg.Topic(), msg.Payload())
+	})
+
+	if token.Wait() && token.Error() != nil {
+		return token.Error()
+	}
+
+	return nil
+}
+
+func (c *client) Disconnect() {
+	c.cli.Disconnect(250)
+}