fix(monitoring): parse wrapped tenant server info

[GatewayJ]

Type of Change

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

Related Issues

Fixes #199

Summary of Changes

• Deserialize the RustFS server-info response envelope before reading Tenant storage data.
• Require the top-level info field instead of silently accepting an empty server-info snapshot.
• Update the server-info regression test to use the response shape returned by RustFS 1.0.0-beta.10.

The Operator previously parsed the entire /rustfs/admin/v3/info response as the inner server-info object. Since the modeled fields have Serde defaults, the response envelope was accepted as an empty value and the poll was reported as successful with every derived Tenant metric set to zero.

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 (N/A; no documentation change is required)
• CHANGELOG.md updated under [Unreleased] (not updated)
• CI/CD passed (pending)

Impact

• Breaking change (CRD/API compatibility)
• Requires doc/config/deployment update
• Other impact: Restores non-zero Operator-derived Tenant storage health and capacity metrics.

Verification

make pre-commit

Additional Notes

No configuration or CRD changes are required.

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[GatewayJ]

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