Create Apache Pulsar producers and consumers with all subscription types

Steps

1. Create a Pulsar client with PulsarClient.builder().serviceUrl('pulsar://...').build().
2. Create a producer: client.newProducer().topic('persistent://tenant/namespace/topic').create(); send messages with producer.send(payload).
3. Create a consumer: client.newConsumer().topic('...').subscriptionName('my-sub').subscriptionType(SubscriptionType.Shared).subscribe(). Choose the subscription type: Exclusive (single active consumer), Shared (round-robin across consumers, no ordering), Failover (one active, others on standby with ordering), Key_Shared (messages with the same key always go to the same consumer).
4. Call consumer.receive() in a loop, process the message, then call consumer.acknowledge(msg) on success.
5. Close producer and consumer when done to release resources.