feat: implement trasaction and anti-frud services

[jaggervlad]

Summary

Implementation of the Yape Code Challenge: a single Spring Boot 3.5.10 application (Java 17) with hexagonal architecture containing two bounded contexts — Transaction and
Anti-Fraud — communicating asynchronously via Apache Kafka.

Features Implemented

Core

• REST API — POST /api/transactions (create) and GET /api/transactions/{id} (retrieve with resolved status)
• Kafka async flow — Transaction publishes to transaction-created, Anti-Fraud validates and publishes result to transaction-status
• Anti-Fraud rule — Transactions with value > 1000 are rejected, all others approved
• PostgreSQL persistence with Spring Data JPA

Production Readiness

• Idempotent Kafka consumers — Safe retries: duplicate messages are no-ops, only real conflicts throw exceptions
• Redis caching for transaction lookups
• Structured JSON logging — Human-readable in dev, JSON (LogstashEncoder) in prod via SPRING_PROFILES_ACTIVE=prod
• Docker Compose with healthchecks on postgres, kafka, and redis + app service with depends_on: service_healthy
• Global exception handling with proper HTTP status codes and validation error responses
• Kafka DLT (Dead Letter Topic) for failed messages
• Spring Actuator health endpoint

Documentation & Quality

• OpenAPI / Swagger UI at /api/swagger-ui.html
• 28 tests — Unit tests (domain model, application services), integration tests (EmbeddedKafka + H2)
• Hexagonal architecture — Domain logic is framework-agnostic with clear port/adapter separation

Tech Stack

Component	Technology
Language	Java 17
Framework	Spring Boot 3.5.10
Build	Maven (with wrapper)
Database	PostgreSQL 14
Cache	Redis 7
Messaging	Apache Kafka
Testing	JUnit 5, EmbeddedKafka, H2, Awaitility
Logging	Logback + logstash-logback-encoder
Docs	springdoc-openapi
Containerization	Docker multi-stage build

How to Run

# Start everything (postgres, kafka, redis, app)
docker-compose up --build

# Verify
curl http://localhost:8080/api/actuator/health

# Create a transaction
curl -X POST http://localhost:8080/api/transactions \
  -H "Content-Type: application/json" \
  -d '{
    "accountExternalIdDebit": "550e8400-e29b-41d4-a716-446655440000",
    "accountExternalIdCredit": "550e8400-e29b-41d4-a716-446655440001",
    "tranferTypeId": 1,
    "value": 120
  }'

# Retrieve (use the transactionExternalId from the response above)
curl http://localhost:8080/api/transactions/{id}

Test Plan

- 28 unit and integration tests passing (./mvnw clean test)
- docker-compose up --build — all services start healthy
- POST /api/transactions with value ≤ 1000 → status becomes approved
- POST /api/transactions with value > 1000 → status becomes rejected
- GET /api/transactions/{id} returns resolved transaction with correct status