User Story

As a developer configuring the Kafka outbox transport, I want a KafkaTransportOptions class with configurable partition count, replication factor, topic auto-creation, and message retention, so that I can tune Kafka topic behavior without modifying transport internals.

Background

KafkaMediatorConfiguratorExtensions.UseKafkaTransport() accepts no options. KafkaMessageTransport creates topics with hard-coded DefaultPartitionCount = 1 and DefaultReplicationFactor = 1. All other Pulse transports (RabbitMqTransportOptions, AzureServiceBusTransportOptions, DaprMessageTransportOptions) provide a dedicated options class. Kafka is the sole exception.

Requirements

• Create KafkaTransportOptions in NetEvolve.Pulse.Kafka:

  public sealed class KafkaTransportOptions
  {
      public int DefaultPartitionCount { get; set; } = 1;
      public short DefaultReplicationFactor { get; set; } = 1;
      public bool AutoCreateTopics { get; set; } = true;
      public TimeSpan? MessageRetention { get; set; }
  }

• Update KafkaMessageTransport to inject IOptions<KafkaTransportOptions> and use the configured values for topic creation.
• Extend UseKafkaTransport() with Action<KafkaTransportOptions>? configureOptions = null parameter and register options accordingly.

Acceptance Criteria

• KafkaTransportOptions properties have documented defaults matching the current hard-coded values.
• KafkaMessageTransport uses options.DefaultPartitionCount and options.DefaultReplicationFactor for topic creation.
• When AutoCreateTopics = false, topic creation is skipped.
• MessageRetention is applied to the topic config when set.
• UseKafkaTransport() without a configure delegate behaves identically to the current implementation.
• Unit tests cover: custom partition count, custom replication factor, AutoCreateTopics = false, custom retention.

Out of Scope

• Per-topic options overrides.
• Consumer group configuration.