Spring Boot Resilience4j

This adds Resilience4j fault tolerance patterns to Spring Boot 3.x services with circuit breakers, retries, rate limiters, bulkheads, and time limiters. You get annotation-based implementations for all the major patterns, plus fallback handling and exponential backoff for retries. The setup requires adding AOP and Actuator dependencies, then you can stack multiple patterns on the same method when you need layered protection. Configuration lives in application.yml with sensible defaults for sliding windows, failure thresholds, and wait durations. Honestly, the real value is in the fallback examples, which show you exactly how to degrade gracefully when services fail instead of just throwing exceptions up the stack.