fix: redact STS credential field aliases

[GatewayJ]

Type of Change

• New Feature
• Bug Fix
• Documentation
• Performance Improvement
• Test/CI
• Refactor
• Other:

Related Issues

Follow-up to PR review feedback on #180: #180 (comment)

Summary of Changes

• Add STS credential field aliases (AccessKeyId, SecretAccessKey) to upstream error redaction.
• Cover both key/value summaries and XML tag redaction before RustFS upstream response bodies are surfaced in operator errors.
• Extend sanitizer and RustFS client error summary tests for the STS credential field names.

Checklist

• I have read and followed the CONTRIBUTING.md guidelines
• Passed make pre-commit (fmt-check + clippy + test + console-lint + console-fmt-check)
• Added/updated necessary tests
• Documentation updated (if needed; N/A)
• CHANGELOG.md updated under [Unreleased] (if user-visible change; N/A)
• CI/CD passed (if applicable)

Impact

• Breaking change (CRD/API compatibility)
• Requires doc/config/deployment update
• Other impact: prevents STS credential values from appearing in upstream error details.

Verification

cargo test redacts_sts_credential_field_names
cargo test unexpected_status_redacts_sensitive_upstream_error_summary
git diff --check
make pre-commit

Additional Notes

This keeps the existing redaction approach intact and only extends the sensitive-key aliases used by the existing match paths.

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