set up consumer group related models

[Dave Shoup (shouples)]

Summary of Changes

No functional changes here, just adding the basic ConsumerGroup, Consumer models with *TreeItem siblings for each before the view provider starts using them with the previously-merged data-fetching operations.

⚠️ Glaring gap in this modeling is the lack of topic/partition data associated with consumers -- this will be handled in a separate branch for #3301 that will add an assignments property and integrate that part of the fetching logic.

Closes #3299

Associated PRs

• add consumer groups icon #3262
  • set up consumer group related models #3263 👈
    • set up ResourceContainer for Flink database and Kafka cluster child resources #3292

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?

[Dave Shoup (shouples)]

Moved to src/icons.ts

[Dave Shoup (shouples)]

Not used by anything yet, just prep for upcoming commands

[Copilot]

Pull request overview

This PR sets up the foundational model classes for Consumer Groups and Consumer members to support the upcoming Consumer Groups view. It introduces ConsumerGroup and Consumer model classes along with their corresponding *TreeItem representations, following the established patterns in the codebase. The PR also refactors the ERROR_ICON constant from flinkDatabaseResourceContainer.ts to icons.ts for better reusability across the codebase.

Changes:

• Added ConsumerGroup and Consumer models with comprehensive properties including state management, membership tracking, and CCloud URL generation
• Added ConsumerGroupTreeItem and ConsumerTreeItem classes with state-based icon coloring and detailed tooltips
• Refactored ERROR_ICON to centralized icons.ts location
• Added test fixtures and comprehensive unit tests covering all model behaviors

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/models/consumerGroup.ts	New model classes for ConsumerGroup and Consumer with TreeItem representations, state management, and URL generation
src/models/consumerGroup.test.ts	Comprehensive unit tests for all model behaviors including state transitions, URL generation, and tree item rendering
tests/unit/testResources/consumerGroup.ts	Test fixtures providing factory functions and pre-configured test instances for all connection types
src/icons.ts	Added ERROR_ICON constant for reuse across models
src/models/flinkDatabaseResourceContainer.ts	Updated to import ERROR_ICON from centralized location
src/models/flinkDatabaseResourceContainer.test.ts	Updated imports to reference ERROR_ICON from centralized location
src/extension.ts	Added comments explaining why consumer groups can't be included in static context value arrays

[sonarqube-confluent]

Quality Gate passed

Issues
1 New issue
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
97.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube

[Lucia Cerchie (Cerchie)]

This LGTM, I did run Claude against it and it had one nit, that these are missing JSDocs:

    `ConsumerGroup.id` getter
    `ConsumerGroup.hasMembers` getter (has inline comment but no JSDoc)
    `ConsumerGroup.searchableText()`
    `ConsumerGroup.ccloudUrl` getter
    `Consumer.id` getter
    `Consumer.searchableText()`
    `Consumer.ccloudUrl` getter

but given how clear the names of these are I'm not going to block on that