docs: link source field to S3 access operator notes

[deepak0x]

The source field lists s3 and arn as supported schemes but says nothing about how S3 credentials are handled. Someone writing a config with source: s3://... has no pointer to how authentication works. This came up in coreos/butane#662, where the reporter noted the Butane spec docs, which are generated from this schema, are silent on S3 credentials.

This adds a sentence to the source description in config/doc/ignition.yaml pointing at the AWS S3 access operator notes. That page already documents the supported URL formats (s3:// and arn:...) and how credentials get resolved: the instance IAM role inside EC2, anonymous otherwise. A maintainer suggested fixing it here first so Butane picks it up on the next vendor bump.

I regenerated the versioned docs with the doc generator. The sentence lands on every source field across all specs. Older specs keep their reduced scheme list (s3 only before 3.2.0, no arn before 3.4.0) because the version transforms are left untouched.

Addresses coreos/butane#662

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📥 Commits

Reviewing files that changed from the base of the PR and between a8fa306 and dfa06df.

📒 Files selected for processing (9)

• config/doc/ignition.yaml
• docs/configuration-v3_0.md
• docs/configuration-v3_1.md
• docs/configuration-v3_2.md
• docs/configuration-v3_3.md
• docs/configuration-v3_4.md
• docs/configuration-v3_5.md
• docs/configuration-v3_6.md
• docs/configuration-v3_7_experimental.md

📜 Recent review details

🧰 Additional context used

📓 Path-based instructions (2)

config/**

⚙️ CodeRabbit configuration file

config/**: The config/ directory is the frontend stable library API consumed by external programs (e.g., Butane). API-breaking changes require bumping the Ignition major version. Ensure backward compatibility.

Files:

• config/doc/ignition.yaml

docs/**

⚙️ CodeRabbit configuration file

docs/**: Documentation served via GitHub Pages/Jekyll. Every platform must be documented in supported-platforms.md. The ./test script validates doc consistency.

Files:

• docs/configuration-v3_1.md
• docs/configuration-v3_2.md
• docs/configuration-v3_6.md
• docs/configuration-v3_7_experimental.md
• docs/configuration-v3_0.md
• docs/configuration-v3_5.md
• docs/configuration-v3_3.md
• docs/configuration-v3_4.md

🔇 Additional comments (9)

config/doc/ignition.yaml (1)

4-4: LGTM!

docs/configuration-v3_0.md (1)

19-23: LGTM!

Also applies to: 32-32, 66-71

docs/configuration-v3_1.md (1)

19-27: LGTM!

Also applies to: 40-40, 83-91

docs/configuration-v3_2.md (1)

19-27: LGTM!

Also applies to: 40-40, 84-92, 131-131

docs/configuration-v3_3.md (1)

19-27: LGTM!

Also applies to: 40-40, 84-92, 131-131

docs/configuration-v3_4.md (1)

19-27: LGTM!

Also applies to: 40-40, 84-92, 131-131

docs/configuration-v3_5.md (1)

19-27: LGTM!

Also applies to: 40-40, 84-92, 131-131

docs/configuration-v3_6.md (1)

19-27: LGTM!

Also applies to: 40-40, 84-92, 131-131

docs/configuration-v3_7_experimental.md (1)

21-29: LGTM!

Also applies to: 42-42, 86-94, 133-133

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📝 Walkthrough

Walkthrough

Configuration schema and versioned documentation now include AWS S3 URL formats, access references, and credential-resolution guidance for remote configuration, certificate, file, fragment, and LUKS key-file sources.

Changes

AWS S3 source documentation

Layer / File(s)	Summary
Source URL guidance config/doc/ignition.yaml, docs/configuration-v3_*.md, docs/configuration-v3_7_experimental.md	Merge and replacement source descriptions document AWS S3 URL formats, access references, and credential resolution.
Certificate source guidance docs/configuration-v3_*.md, docs/configuration-v3_7_experimental.md	TLS certificate source descriptions include AWS S3 access guidance.
File and key source guidance docs/configuration-v3_*.md, docs/configuration-v3_7_experimental.md	File, appended-fragment, and LUKS key-file descriptions include AWS S3 access references and credential guidance.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title uses the required subsystem format, starts with a lowercase imperative description, and accurately describes the documentation change.
Description check	✅ Passed	The description clearly explains the S3 documentation update, credential guidance, regenerated versioned docs, and related issue.
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.
Commit Message Convention	✅ Passed	The PR has one non-merge commit: docs: link source field to S3 access operator notes. It uses a valid subsystem, lowercase imperative description, and no period.

✨ Finishing Touches

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• Create PR with unit tests

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