feat(transactions): add idempotency support and optimistic versioning

[jeanc80]

Summary

This pull request introduces idempotency handling and optimistic versioning for transactions to prevent duplicate processing and ensure data consistency.

Key changes

• Added idempotency_key, request_hash, and version columns to transactions table
• Created unique partial index for idempotency enforcement
• Implemented automatic createdAt initialization with @PrePersist
• Updated persistence layer to support idempotent operations
• Rebuilt Docker environment and synchronized schema migrations

Technical details

• Flyway/Liquibase migrations: V4, V5
• Database: transactions table
• Constraint: unique index on idempotency_key (when not null)

Testing

• Environment rebuilt using docker compose
• Idempotency validated via Postman by sending repeated requests with the same idempotency key
• Verified that duplicated requests do not generate new records

Impact

• Prevents duplicated financial transactions
• Improves system resilience and API reliability
• No breaking changes to public API

Checklist

• Database migrations executed successfully
• Docker environment rebuilt
• Idempotency behavior tested
• No breaking API changes

Author

Jean Carlos Flores León
Senior Software Engineer
GitHub: @jeanc80