feat: add backend_v1 migration

backend_v1/app/events/subscribers/utils.go

@@ -0,0 +1,24 @@
+package subscribers
+
+import (
+	"encoding/json"
+
+	"github.com/ThreeDotsLabs/watermill"
+	"github.com/ThreeDotsLabs/watermill/message"
+)
+
+func toMessage(event any) (*message.Message, error) {
+	b, err := json.Marshal(event)
+	if err != nil {
+		return nil, err
+	}
+	return message.NewMessage(watermill.NewUUID(), b), nil
+}
+
+func toMessageList(event any) ([]*message.Message, error) {
+	m, err := toMessage(event)
+	if err != nil {
+		return nil, err
+	}
+	return []*message.Message{m}, nil
+}