v1.2.0 - Refactor & Test Coverage

Changelog

Refactor

• Replace CopyOnWriteArrayList with ConcurrentHashMap in RedisManager for client storage
• registerClient now returns @NotNull and uses case-insensitive key matching to prevent duplicate IDs
• Remove CompletableFuture usage in RedisClient and simplify topic handling
• Move TimedRequestSerializer from net.bitbylogic.rps.gson to net.bitbylogic.rps
• Reduce TimedRequestSerializer access level to package-private
• Change null channel fallback to empty string in TimedRequestSerializer
• Introduce static shared GSON instance in ListenerComponent with enableComplexMapKeySerialization()
• Remove pretty printing from RedisManager GSON instance
• Change ListenerComponent(targetServerId, channel) constructor from private to public
• Change setAllowSelfActivation() from private to protected in RedisMessageListener
• Add @Contract annotations to fluent methods in ListenerComponent
• Add @CheckReturnValue to getData, getDataOrElse, and getRequestByID in ListenerComponent
• Add @CheckReturnValue to RedisManager#registerClient

Style

• Fix Javadoc paragraph formatting in RedisClient

Tests

• Add RedisManagerTest using JUnit 5 and TestContainers
• Add test coverage for duplicate client registration, message send/receive, self-activation, multiple listeners, server ID filtering, timed request timeout/success, and malformed JSON handling
• Add maven-surefire-plugin, junit-jupiter, and testcontainers-redis dependencies