Feat/idr rate aggregator by thaufan

[thaufaniqbal]

Summary

This PR implements the Strategy Pattern for IDR-related data fetchers and sets up the main service with spread factor calculation. It ensures modularity, testability, and clean architecture for the Finance API.

Changes

• Added strategy classes:
  • LatestIdrRatesFetcher (with spread factor calculation)
  • HistoricalIdrUsdFetcher
  • SupportedCurrenciesFetcher
• Configured WebClient via FactoryBean with base URL and timeout
• Implemented USD_BuySpread_IDR calculation using personalized spread factor (0.00264)
• Built FinanceDataStore as a thread-safe immutable in-memory store
• Added ApplicationRunner for startup data initialization
• Implemented MDC Trace Filter for request tracing
• Added exception handling with custom ResourceNotFoundException
• Updated README with setup, usage examples, and endpoint documentation
• Added unit and integration tests (JUnit 5, Mockito, WireMock)

Testing

• Verified endpoints via cURL/Postman:
  • /api/finance/data/latest_idr_rates
  • /api/finance/data/historical_idr_usd
  • /api/finance/data/supported_currencies
• Spread factor calculation matches requirements
• All unit and integration tests passed (mvn test)

Notes

• Health check and app info available via Spring Boot Actuator
• H2 in-memory database console enabled for inspection
• Code structured to be modular, maintainable, and easily extensible for new resource types