[NEB-4778] Add KYC, geo, and bot-detection structured fields

[rkumar-sift]

Purpose

Add support for the new structured fields ($nationality, $year_of_birth, $kyc, $geo, $bot_identification) per the Structured Fields TDD (NEB-4573).

Summary

• New model classes Kyc, Geo, BotIdentification under Sift/Schema/ComplexTypes/.
• Wired into create_account/update_account (all 5 fields), verification ($kyc only), transaction, create_order/update_order ($kyc/$geo/$bot_identification), login ($geo/$bot_identification only).
• Enum-valued fields ($kyc_level, $bot_identification.$result) use $-prefixed string values ($basic/$full, $human/$bot/$suspected), consistent with other enum fields in this API (e.g. $login_status).
• Version bump 1.7.0 → 1.8.0, CHANGES.MD/README.md updated.

Testing

• The change was thoroughly tested manually
• The change was covered with unit tests
• The change was tested with real API calls
• Necessary changes were made in the integration tests
• New functionality is reflected in README

Update 2026-09-02

Server-side dependency (NEB-4775) is now merged and deployed to production, so added the deferred integration test coverage: Test.Integration.Net and Test.Integration.NetFx48 fixtures now include the new fields. Test.Integration.Net fully verified against real prod. Test.Integration.NetFx48 could not be executed locally (no ARM64 macOS testhost exists for net48, and the Mono-based workaround hits a native runtime segfault on Apple Silicon) — build is clean and content is identical to the verified Test.Integration.Net version; will rely on CI for direct execution confirmation there.

[mzobro-sift]

LGTM, please do not merge until https://github.com/SiftScience/code/pull/63932 is merged and deployed

[mzobro-sift]

LGTM