fix(site-explorer): generate BF4 machine IDs from chassis serial

[poroh]

Use the BlueField_BMC chassis serial as a DPU fallback when the
Redfish system serial is absent, and add BF4 mock coverage for machine
ID generation.

Related issues

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• No testing required (docs, internal refactor, etc.)

Additional Notes

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

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📥 Commits

Reviewing files that changed from the base of the PR and between 50a097b and 678715a.

📒 Files selected for processing (3)

• crates/api-model/src/site_explorer/mod.rs
• crates/bmc-explorer/tests/bluefield4_explore.rs
• crates/bmc-mock/src/test_support/mod.rs

🚧 Files skipped from review as they are similar to previous changes (3)

• crates/bmc-explorer/tests/bluefield4_explore.rs
• crates/api-model/src/site_explorer/mod.rs
• crates/bmc-mock/src/test_support/mod.rs

---

Summary by CodeRabbit

• Bug Fixes

  • Improved DPU machine ID generation by trimming/validating the primary system serial and treating missing/blank values as absent.
  • When the primary serial is unusable, the machine ID now correctly falls back to the Bluefield_BMC chassis serial.

• Tests

  • Added an integration test for BlueField4 exploration to verify endpoint type/vendor, chassis serial handling, and consistent machine ID output.
  • Added a dedicated test-support helper to build the mocked BlueField4 BMC setup.

Walkthrough

MachineId generation now falls back to a Bluefield_BMC chassis serial for DPUs when the system serial is absent. BlueField4 test support and integration coverage were added for this path.

Changes

BlueField4 MachineId fallback

Layer / File(s)	Summary
MachineId serial selection crates/api-model/src/site_explorer/mod.rs	generate_machine_id() now uses a helper that prefers the first system serial and falls back to the Bluefield_BMC chassis serial for DPU endpoints when needed.
BlueField4 test coverage crates/bmc-mock/src/test_support/mod.rs, crates/bmc-explorer/tests/bluefield4_explore.rs	A new test-support helper builds a BlueField4 BMC handle from DpuMachineInfo, and the integration test validates the report shape, chassis data, firmware inventory, and generated machine ID.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• NVIDIA/infra-controller#2902: Adds the BlueField4 mock scaffolding that this PR’s new test helper and integration test build on.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: BF4 machine IDs now derive from the chassis serial fallback.
Description check	✅ Passed	The description is directly aligned with the change set and test coverage for BF4 machine ID generation.
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

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• Create PR with unit tests

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Actionable comments posted: 1

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Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@crates/api-model/src/site_explorer/mod.rs`:
- Around line 886-901: Treat blank Redfish system serials as missing in
machine_id_serial_number before the BF4 fallback runs. Update the
self.systems.first().and_then(|system| system.serial_number.as_ref()) path to
also reject empty or whitespace-only values, matching the chassis serial
filtering used for Bluefield_BMC. Keep the fallback logic in
machine_id_serial_number and generate_machine_id() unchanged so BF4 reports with
blank system serials can still resolve via the chassis serial.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: c80c5434-d508-40ee-bf71-0bc3695073d3

📥 Commits

Reviewing files that changed from the base of the PR and between 2acb7c3 and 45c683b.

📒 Files selected for processing (3)

• crates/api-model/src/site_explorer/mod.rs
• crates/bmc-explorer/tests/bluefield4_explore.rs
• crates/bmc-mock/src/test_support/mod.rs

[github-actions]

🔍 Container Scan Summary

Service	Total	Critical	High	Medium	Low	Other
boot-artifacts-aarch64	3	0	0	3	0	0
boot-artifacts-x86_64	3	0	0	3	0	0
forge-admin-cli-x86_64	285	6	26	102	7	144
machine-validation-runner	744	32	188	267	36	221
machine_validation	744	32	188	267	36	221
machine_validation-aarch64	744	32	188	267	36	221
nvmetal-carbide	744	32	188	267	36	221
TOTAL	3267	134	778	1176	151	1028

Per-CVE detail lives in the per-service grype-* artifacts (JSON + SARIF). Severity counts only — no CVE IDs published here.