Add tests for all enums, request builders, and response types in
the MAS FEAT compliance module to improve coverage.

Replace List<String> with List<Finding> for type safety.
Add FEATPillar, FindingSeverity, FindingStatus enums.
Finding includes: id, pillar, severity, category, description,
status, remediation, dueDate.

Add MASFEATNamespace inner class with all MAS FEAT API methods:

Registry:
- registerSystem, activateSystem, getSystem, getRegistrySummary

Assessments:
- createAssessment, getAssessment, updateAssessment
- submitAssessment, approveAssessment, rejectAssessment

Kill Switch:
- getKillSwitch, configureKillSwitch, triggerKillSwitch
- restoreKillSwitch, getKillSwitchHistory

Includes field name mapping (customerImpact → risk_rating_impact, etc.)
and response parsing with alternate field name handling.

…pesTest

- Switch from MockWebServer to WireMock (consistent with project)
- Fix activateSystem test to match PUT /registry/{id} endpoint
- Fix method signatures (approveAssessment, restoreKillSwitch, etc)
- Remove listSystems test (method not implemented yet)
- Use string comparison for KillSwitchEvent eventType