Add redis: Boot 4.1 + Spring Data Redis 4.1, the JDK-serialisation default vs Jackson 3 serializers, @RedisHash TTL and keyspace events, @RedisListener, and Redis as the Spring cache

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3

redis/docs/output/12-pub-sub-lost-message.txt

@@ -0,0 +1,20 @@
+# Pub/Sub is at-most-once: a stopped listener loses messages
+
+
+--- Stop the listener container, then publish ---
+container.stop()
+$ redis-cli -p 6390 --no-raw PUBSUB NUMSUB news
+1) "news"
+2) (integer) 0
+template.convertAndSend("news", "while you were away") = 0 receivers
+
+--- Start it again ---
+container.start()
+$ redis-cli -p 6390 --no-raw PUBSUB NUMSUB news
+1) "news"
+2) (integer) 1
+messages the listener has: []
+
+--- Once it is back, messages flow again ---
+template.convertAndSend("news", "welcome back") = 1 receiver
+@RedisListener got 'welcome back'