[FLINK-39788][kubernetes] Append .svc suffix to namespaced Kubernetes service hostnames

[wilmerdooley]

What is the purpose of the change

When a Flink Session cluster is deployed on Kubernetes, the TaskManager resolves the JobManager RPC endpoint through Pekko using the value returned by getNamespacedServiceName (and its related helpers). The current implementation produces a hostname of the form <service>.<namespace>, which is not a fully qualified Kubernetes service DNS name and is treated as an opaque host by Pekko. For namespaces whose name begins with a digit (for example 1234-ns), DNS resolution fails and the TaskManager logs Actor not found while trying to connect to the dispatcher (FLINK-39788).

This change appends the .svc segment so the namespaced service name becomes the standard Kubernetes service FQDN <service>.<namespace>.svc, which resolves correctly regardless of how the namespace name begins.

Brief change log

• Append .svc to the namespaced service name in ExternalServiceDecorator.getNamespacedExternalServiceName, InternalServiceDecorator.getNamespacedInternalServiceName, and KubernetesUtils.getNamespacedServiceName, so the result is the FQDN <service>.<namespace>.svc.
• Update the expected address in KubernetesClusterDescriptorTest to match the new fully qualified host.

Verifying this change

This change is already covered by existing tests, specifically KubernetesClusterDescriptorTest.testDeployApplicationClusterWithClusterIP, whose expected web interface URL is updated to assert the new <service>.<namespace>.svc hostname.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: yes (changes the Kubernetes service hostname used for JobManager RPC resolution)
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

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Generated-by: Claude Code

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CI report:

• 933712f Azure: FAILURE

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