Test GET /, server info.

[dblock]

Description

• Adds tests for GET /.
• Makes build_flavor optional. It was deprecated during the fork and removed in 2.x AFAIK. The added test trips on this. Yay tests.
• Renames index_lifecycle to index, I think we should stick to naming that closely matches the API.

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[github-actions]

Changes Analysis

Commit SHA: 9eaf6be
Comparing To SHA: f486e8b

API Changes

Summary

└─┬Components
  └─┬_common:OpensearchVersionInfo
    └──[➖] required (26493:11)❌ 

Document Element	Total Changes	Breaking Changes
components	1	1

• ❌ BREAKING Changes: 1 out of 1
• Removals: 1
• Breaking Removals: 1

Report

The full API changes report is available at: https://github.com/opensearch-project/opensearch-api-specification/actions/runs/9356254214/artifacts/1564099224

API Coverage

	Before	After	Δ
Covered (%)	476 (46.62 %)	476 (46.62 %)	0 (0 %)
Uncovered (%)	545 (53.38 %)	545 (53.38 %)	0 (0 %)
Unknown	24	24	0