Log health contributor statuses when Eureka health status changes

[yashdotdev13]

Summary

Adds logging of individual health contributor statuses when the aggregated Eureka health status changes.

The health check handler now collects contributor names and their corresponding statuses while evaluating blocking and reactive health contributors. The collected statuses are included in the log message together with the resulting Eureka InstanceStatus.

Composite blocking and reactive health contributors continue to be traversed recursively, with their individual contributor names preserved.

Changes

• Collect health contributor statuses by name during health evaluation.
• Log the resulting Eureka health status together with contributor statuses when the status differs from the current InstanceStatus.
• Preserve the existing status aggregation behavior by aggregating the collected statuses.
• Add test coverage for named blocking health indicators.
• Add test coverage for named reactive health indicators.

Testing

./mvnw.cmd -pl spring-cloud-netflix-eureka-client -DskipTests compile
./mvnw.cmd -pl spring-cloud-netflix-eureka-client -Dtest=EurekaHealthCheckHandlerTests test

[ryanjbaxter]

Why are you still aggregating status then in the other methods?

[yashdotdev13]

The aggregation in getStatus is still required to determine the overall Eureka health status via StatusAggregator. The change only moves logging of each contributor's individual status into processContributor; the aggregated result remains necessary for computing the final overall status.

[ryanjbaxter]

Cherry picked into 5.0.x as well