As a Swatch developer, I want to enable Swatch to consume from the new Kafka topic in parallel with the existing UMB topic (VirtualTopic.services.partner-entitlement-gateway).   I want the new kafka consumer to invoke the same downstream codepath as the legacy consumer so that contract updates behave consistently, regardless of which consumer processes a message first.

This is the same pattern to what we did in SWATCH-3456, except instead of UMB > UMB, we're doing UMB>Kafka

Effort Considerations:

• Unknown: Any changes to the message format. Not just fields getting passed, but if it's still XML in the payload. Need to check upstream IT Partner Gateway work to get that answer.
• swatch-contracts already has kafka libraries, but UMB isn't 1-to-1 with Kafka, so application.properties changes and configuration values need to be considered (i.e. consumer groups, failure handling strategy, batching, etc.
• Do we need to add an additional SSL/TLS Configuration or will our usual trust/keystore "just work"

Acceptance Criteria:

• swatch-contracts subscribes to the new kafka topic alongside the legacy umb topic
• logging should distinguish which topic a message is being consumed from
• messages from the new topic use the same logic as messages consumed from the legacy topic
• validate that both consumers result in consistent updates to contract entities
• testing should include test cases that:
  • new consumer receives a message before the legacy one
  • legacy consumer receiving a message before the new one
  • both consumers receive the same message in close succession