docs(design): DPU Extension Service DPF Helm Chart type

[hanyux-nv]

Add a design doc for DPU extension service integration with DPF. The design describes how tenant-created extension services can be installed through the DPF Helm service lifecycle while only running on DPUs selected by instance attachments.

Related issues

Related to #3103

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 356dd0b and 39890f8.

📒 Files selected for processing (1)

• docs/design/dpf-helm-chart-extension-services.md

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Summary by CodeRabbit

• Documentation
  • Added a design document for a new tenant extension service option backed by Helm charts.
  • Describes the end-to-end lifecycle for creating, attaching, updating, detaching, and deleting chart-based services.
  • Covers version tracking, deployment status, validation rules, attachment targeting, and compatibility handling.

Walkthrough

Adds a new design document proposing a DPF_HELM_CHART extension service type. It covers proto/API additions, new database tables for reconciliation and attachment tracking, controller-driven create/attach/update/detach/delete workflows, credential handling, testing requirements, operational considerations, and open questions.

Changes

Design Document

Layer / File(s)	Summary
Problem statement and scope docs/design/dpf-helm-chart-extension-services.md	Adds title, motivation, high-level mechanism, and explicit goals/non-goals for the DPF_HELM_CHART service type, preserving existing KUBERNETES_POD behavior.
API and proto contract changes docs/design/dpf-helm-chart-extension-services.md	Defines the new service type enum, dpf_helm_chart_credentials field, credential purpose model, JSON schema/version validation rules, and deployment_status field on version info.
Database schema for reconciliation and attachment tracking docs/design/dpf-helm-chart-extension-services.md	Specifies dpf_extension_service_reconciliations and dpf_extension_service_attachments tables with state fields, constraints, and indexes.
Create, reconciliation, and attach/detach/delete workflows docs/design/dpf-helm-chart-extension-services.md	Documents the API/controller create flow, DPUDeployment integration, label-based attach targeting, per-DPU status mapping, and update/detach/delete gating semantics.
Credential handling, testing, and operational concerns docs/design/dpf-helm-chart-extension-services.md	Covers credential manager secret paths, required test coverage and definition-of-done checklist, RBAC/rollout considerations, drawbacks/alternatives, unresolved questions, and future extensions.

Estimated code review effort: 2 (Simple) | ~15 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is specific and aligned with the new DPF Helm Chart design document.
Description check	✅ Passed	The description accurately describes the design doc and its DPF Helm-based extension service workflow.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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