Add rate-limit module: Bucket4j 8.21 token buckets on Redis in a Spring Boot 4.1 filter, per-user/per-key/global limits, 429 with Retry-After, two instances sharing one bucket

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b7rnC7jppGGdHGESvy

rate-limit/output/08-two-jvms.txt

@@ -0,0 +1,23 @@
+== two JVMs (A on 8081, B on 8082), one redis-server on 6411; free-key-123 allows 5 per minute
+request 1 to :8081 -> 200
+request 2 to :8082 -> 200
+request 3 to :8081 -> 200
+request 4 to :8082 -> 200
+request 5 to :8081 -> 200
+request 6 to :8082 -> 429
+
+$ curl -si -H 'X-API-Key: free-key-123' http://localhost:8081/api/hello
+HTTP/1.1 429 
+X-RateLimit-Limit: 5
+X-RateLimit-Remaining: 0
+X-RateLimit-Reset: 60
+X-RateLimit-Scope: api-key
+Retry-After: 12
+Content-Type: application/problem+json
+
+{"type":"about:blank","title":"Too Many Requests","status":429,"detail":"Rate limit exceeded for scope 'api-key'. Retry in 12 second(s).","retryAfterSeconds":12}
+
+
+$ redis-cli -p 6411 --scan
+rl:global
+rl:key:ea39d5800282edc4