docs: pipeline: outputs: s3: document S3-compatible endpoints

[goanpeca]

The endpoint description in the configuration parameters table doesn't say what a custom endpoint is for, even though the page later shows MinIO and Google Cloud examples that rely on it. This expands the description to state that endpoint points the S3 output at an S3-compatible object store other than Amazon S3, and adds the two behaviors that matter when you do that.

Both behaviors come from the plugin source. s3_put_object builds the request URI as /<bucket><key> while cb_s3_init sets the client host to the configured endpoint, so requests are always path-style rather than virtual-hosted. cb_s3_init also sets s3_client->region from region, which flb_signv4_do in src/aws/flb_aws_util.c uses for the SigV4 credential scope, so region still matters when the endpoint isn't an AWS one.

No other changes: the parameter table stays alphabetical and the existing MinIO and Google Cloud sections are untouched.

Summary by CodeRabbit

• Documentation
  • Expanded S3 endpoint configuration guidance to cover schemes, ports, S3-compatible object stores, path-style requests, and region-based signing.

[coderabbitai]

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Run ID: 27839555-4601-4ddd-bd92-3b82d7e2ce86

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Reviewing files that changed from the base of the PR and between 0eb06a6 and 61cdd12.

📒 Files selected for processing (1)

• pipeline/outputs/s3.md

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📝 Walkthrough

Walkthrough

The S3 output documentation now describes endpoint schemes and ports, S3-compatible object stores, path-style requests, and signing with the configured region.

Changes

S3 endpoint documentation

Layer / File(s)	Summary
Document S3 endpoint behavior pipeline/outputs/s3.md	The endpoint parameter description now covers schemes, ports, S3-compatible services, path-style bucket and key requests, and configured-region signing.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested reviewers: eschabell, rituparnakhaund

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the documentation update for S3-compatible endpoints.
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.

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[eschabell]

@goanpeca I've fixed the lint / vale issues, removing draft status as confirmed the fix is good. I'll review now.

[eschabell]

@goanpeca this is approved, thanks for the docs PR!