- Update BillingSummary.Breakdown field type from map[string]interface{} to map[string]any
- Update Transaction.Metadata field type from map[string]interface{} to map[string]any
- Update RatePlanCurrencyIntegrator subscription and billing metadata to use map[string]any
- Update handler request/response types to use map[string]any (CreateRatePlanRequest, UpdateRatePlanRequest,
- Add Repository interface with tenant CRUD, user management, API keys, usage tracking, config, and event operations
- Add Service interface with tenant management, user operations, API key handling, quota checking, config management, authentication, and analytics methods
- Add Middleware interface with request extraction, access validation, context injection, rate limiting, and resource isolation