Feature Request: Support gRPC Pub/Sub

[Cluas]

Feature request

Please add support for gRPC Pub/Sub in Watermill.

Description

Currently, Watermill's Pub/Sub component does not support the gRPC protocol. Integrating gRPC Pub/Sub would allow Watermill to act as a message broker using efficient gRPC communication, enabling publish/subscribe scenarios in distributed microservices.

Example use case

In distributed microservices, developers want to use Watermill's Pub/Sub API to transmit events across services via gRPC. This would let services written in different languages (as long as they support gRPC) seamlessly publish and consume messages.

How it can look like in code

// Suppose Watermill provides a gRPC PubSub implementation:
pubSub, err := grpcpubsub.New(config)
if err != nil {
  log.Fatal(err)
}

message := message.NewMessage(watermill.NewUUID(), []byte("Hello via gRPC"))
if err := pubSub.Publish("events", message); err != nil {
  log.Fatal(err)
}

// Subscription
go func() {
  messages, err := pubSub.Subscribe(context.Background(), "events")
  if err != nil {
      log.Fatal(err)
  }
  for msg := range messages {
      fmt.Printf("Received message: %s\n", string(msg.Payload))
  }
}()