Publish Discord inbound replies on the post event bus (#19)

Inbound publishes PostCreated after saving the Discord link. Outbound skips already-linked posts so the bot does not echo. Mail uses the existing subscriber.

Reviewed-on: #19
Co-authored-by: codegirl-007 <s.raide@gmail.com>

cmd/server/main.go

@@ -38,7 +38,7 @@ func main() {
 	}
 	bus := events.New()
 	mail.Subscribe(bus, store.NewPostgres(db), notifier)
-	bot, err := discord.FromEnv(store.NewDiscordLinks(db), bus, store.NewPostgres(db), notifier)
+	bot, err := discord.FromEnv(store.NewDiscordLinks(db), bus, store.NewPostgres(db))
 	if err != nil {
 		log.Fatalf("discord: %v", err)
 	}