Highly optimize topic name

src/main/java/it/tdlight/reactiveapi/KafkaProducer.java

@@ -34,10 +34,10 @@ public class KafkaProducer {
 		sender = KafkaSender.create(senderOptions.maxInFlight(1024));
 	}
 
-	public Mono<Void> sendMessages(long userId, Flux<ClientBoundEvent> eventsFlux) {
+	public Mono<Void> sendMessages(UserTopic userId, Flux<ClientBoundEvent> eventsFlux) {
 		return eventsFlux
 				.<SenderRecord<Integer, ClientBoundEvent, Integer>>map(event -> SenderRecord.create(new ProducerRecord<>(
-						"tdlib.event.%d".formatted(userId),
+						userId.getTopic(),
 						event
 				), null))
 				.transform(sender::send)

src/main/java/it/tdlight/reactiveapi/ReactiveApiPublisher.java

@@ -75,6 +75,7 @@ public abstract class ReactiveApiPublisher {
 
 	private final AtomicReference<State> state = new AtomicReference<>(new State(LOGGED_OUT));
 	protected final long userId;
+	protected final UserTopic userTopic;
 	protected final long liveId;
 	private final String dynamicIdResolveSubject;
 
@@ -90,6 +91,7 @@ public abstract class ReactiveApiPublisher {
 		this.eventService = atomix.getEventService();
 		this.resultingEventTransformerSet = resultingEventTransformerSet;
 		this.userId = userId;
+		this.userTopic = new UserTopic(userId);
 		this.liveId = liveId;
 		this.dynamicIdResolveSubject = SubjectNaming.getDynamicIdResolveSubject(userId);
 		this.rawTelegramClient = ClientManager.createReactive();
@@ -197,7 +199,7 @@ public abstract class ReactiveApiPublisher {
 				// Buffer requests to avoid halting the event loop
 				.onBackpressureBuffer();
 
-		kafkaProducer.sendMessages(userId, messagesToSend).subscribeOn(Schedulers.parallel()).subscribe();
+		kafkaProducer.sendMessages(userTopic, messagesToSend).subscribeOn(Schedulers.parallel()).subscribe();
 
 		publishedResultingEvents
 				// Obtain only cluster-bound events

src/main/java/it/tdlight/reactiveapi/UserTopic.java

@@ -0,0 +1,14 @@
+package it.tdlight.reactiveapi;
+
+public class UserTopic {
+
+	private final String value;
+
+	public UserTopic(long userId) {
+		value = "tdlib.event.%d".formatted(userId);
+	}
+
+	public String getTopic() {
+		return value;
+	}
+}