set up ResourceContainer for Flink database and Kafka cluster child resources

[Dave Shoup (shouples)]

Summary of Changes

This PR takes most of the state management that FlinkDatabaseResourceContainer handled to extend into a ResourceContainer abstract base class, allowing a Kafka cluster flavored version that will be used in a downstream branch for "Consumer Group" and "Topics" containers.

Closes #3230

Associated PRs

• set up consumer group related models #3263
  • set up ResourceContainer for Flink database and Kafka cluster child resources #3292 👈
    • show consumer groups in Topics view #3264

Optional: Any additional details or context that should be provided?

While this seems like backpedaling from removing the ContainerTreeItem, the new abstract class helps with icon and context value transitions instead of effectively being a TreeItem with a searchable children array.

Pull request checklist

Please check if your PR fulfills the following (if applicable):

Tests

• Added new
• Updated existing
• Deleted existing

Release notes

• Does anything in this PR need to be mentioned in the user-facing CHANGELOG?

[sonarqube-confluent]

Quality Gate passed

Issues
1 New issue
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
98.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[Copilot]

Pull request overview

Refactors Flink Database container tree-item state management into a reusable ResourceContainer abstract base class, and introduces a Kafka-cluster-oriented container type to support upcoming Topics/Consumer Groups view work.

Changes:

• Added ResourceContainer base class to unify loading/error/children state transitions across container TreeItems.
• Migrated Flink Database containers to src/models/containers/ and updated the Flink Database view provider + tests to use setLoading() / setLoaded() / setError().
• Introduced KafkaClusterResourceContainer (and label enum) plus unit tests, and updated unit-test helpers to support simpler resource creation.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/unit/testResources/base.ts	Makes name optional in test resource helpers and improves fallback searchable text.
src/viewProviders/flinkDatabase.ts	Uses new container state transition methods instead of mutating fields directly.
src/viewProviders/flinkDatabase.test.ts	Updates tests to use setLoaded() rather than assigning children directly.
src/models/flinkDatabaseResourceContainer.ts	Removes the previous Flink-specific container implementation (moved/refactored under containers/).
src/models/flinkDatabaseResourceContainer.test.ts	Removes old Flink container tests (replaced by new container tests).
src/models/containers/resourceContainer.ts	Adds the new shared container base class encapsulating loading/error/children behavior.
src/models/containers/resourceContainer.test.ts	Adds comprehensive unit tests for ResourceContainer state transitions and helper methods.
src/models/containers/kafkaClusterResourceContainer.ts	Adds Kafka-cluster flavored container subclass and label enum for Topics view containers.
src/models/containers/kafkaClusterResourceContainer.test.ts	Adds unit tests validating constructor/id/loggerName behavior for Kafka cluster containers.
src/models/containers/flinkDatabaseResourceContainer.ts	Reintroduces Flink DB container as a thin subclass of ResourceContainer.
src/models/containers/flinkDatabaseResourceContainer.test.ts	Adds focused constructor tests for the Flink DB container subclass.
src/commands/utils/udfRegistration.test.ts	Updates imports to new Flink container location and tightens a Kafka cluster type import.
src/commands/flinkDatabaseView.ts	Updates imports to the new Flink container module path.
src/commands/flinkDatabaseView.test.ts	Updates imports to the new Flink container module path.
src/commands/flinkArtifacts.test.ts	Updates imports to the new Flink container module path.

[James Robinson (jlrobins)]

Looks like a good step towards being able to simplify complex views like FlinkDatabaseViewProvider into managing a list of per-element-type containers that then know the per-element-type smarts.