Implement CLI→library request builder snapshot coverage for CLI↔client contract test coverage

[sdairs]

Parent: #151 — scoping: #165

Summary

Today, crates/clickhousectl/src/cloud/commands.rs has a #[cfg(test)] mod tests block (line ~2030 onwards) that asserts the JSON shape of a handful of build_*_request helpers — build_create_service_request, build_update_service_request, build_api_key_create_request, build_api_key_update_request, build_org_update_request, build_backup_config_update_request, build_query_endpoint_create_request, build_service_password_patch_request.

The coverage is partial and ad-hoc:

• Some helpers have one happy-path test; some only have rejection tests.
• Assertions cherry-pick a few fields (json["tags"][0]["key"], etc) rather than asserting the full serialized shape.
• Optional-vs-required distinctions (camelCase keys absent when Option::None) are not consistently verified.
• New build_*_request helpers can land without any test at all — there's no structural guard.

This issue makes the existing pattern systematic: a single test module that snapshots the full serialized JSON for every build_*_request helper, under both a minimal-required-only and a maximal-all-fields-set input. No new dependencies (no wiremock, no insta); plain assert_eq! against an inline serde_json::json!(...) expected value, so review diffs stay readable.

Scope

• For every build_*_request helper in crates/clickhousectl/src/cloud/commands.rs, add:
  • <helper>_minimal_request_shape — only required CLI args set, assert the complete serialized JSON via serde_json::to_value(&request).
  • <helper>_maximal_request_shape — every optional CLI arg set, assert the complete serialized JSON.
• Keep tests in the same #[cfg(test)] mod tests block (consistent with existing pattern); do not introduce a new tests/ directory yet.
• Each test must use assert_eq!(json, serde_json::json!({ ... })) against the full expected object, so adding a field to the request silently is a compile-time-stable / test-failure regression.
• Replace the cherry-pick assertions in the existing *_supports_* / *_trims_* tests where they duplicate the new full-shape tests.
• Leave the existing *_rejects_* validation tests untouched — they cover input parsing, not request shape.

Out of scope

• Going through clap parsing (covered by the second sub-issue).
• Transport-level testing via wiremock (covered by the second sub-issue).
• CloudClient wrapper methods that don't build a body (GET / DELETE / list) — those have no request shape to assert.

Definition of done

• Every build_*_request helper has a minimal and a maximal full-shape snapshot test.
• A new build_*_request helper that lands without a paired test is caught by reviewer convention — add a one-line comment on the test module documenting the rule.
• cargo test -p clickhousectl passes.
• Single PR, no new dependencies.