Add maintenance notifications support for OSS API cluster clients

[petyaslavova]

Description
Adds support for smart connection hand-off during maintenance operations for Redis Cloud databases with OSS API enabled.
When a cluster node undergoes maintenance, the client automatically updates its cluster topology and manages connections to ensure minimal disruption (in case the feature is enabled in the server).

Changes

• New notification types: OSSNodeMigratingNotification and OSSNodeMigratedNotification for OSS cluster maintenance events (SMIGRATING/SMIGRATED push messages)

• New handler: OSSMaintNotificationsHandler to process cluster-wide maintenance notifications and trigger topology refresh

• Cluster client integration: MaintNotificationsAbstractRedisCluster mixin adds maintenance notification support to RedisCluster

• Connection management: Affected connections are marked for reconnect; removed nodes have their connections disconnected

• Parser updates: Handle new SMIGRATING/SMIGRATED push message types

• Auto-enabled for RESP3: Maintenance notifications are enabled by default when using protocol version 3

Usage

  from redis.cluster import RedisCluster
  from redis.maint_notifications import MaintNotificationsConfig
  
  # Option 1: Auto-enabled with RESP3 (default config)
  client = RedisCluster(host="localhost", port=6379, protocol=3)
  
  # Option 2: Custom configuration
  config = MaintNotificationsConfig(
      enabled=True,
      proactive_reconnect=True,
      relaxed_timeout=30.0
  )
  client = RedisCluster(
      host="localhost", 
      port=6379, 
      protocol=3,
      maint_notifications_config=config
  )

[petyaslavova]

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[augmentcode]

🤖 Augment PR Summary

Summary: Adds Redis Cluster maintenance-notification support for Redis Cloud OSS API clusters (hitless topology refresh & connection handoff) when RESP3 push notifications are enabled.

Changes:

• Introduces OSS-specific maintenance notification types: OSSNodeMigratingNotification and OSSNodeMigratedNotification (SMIGRATING/SMIGRATED).
• Extends RESP3 push parsing to recognize SMIGRATING/SMIGRATED and route them to appropriate handlers.
• Adds OSSMaintNotificationsHandler to refresh cluster topology on SMIGRATED and manage reconnect/disconnect of affected node connections.
• Integrates a new MaintNotificationsAbstractRedisCluster mixin into RedisCluster to wire OSS maintenance handling into all node pools.
• Updates connection/pool maintenance wiring to support an OSS cluster handler alongside existing moving/migrating handlers.
• Auto-enables maintenance notifications for RESP3 in cluster initialization when config is not provided.
• Improves protocol checks via check_protocol_version() and fixes slot=0 handling by using slot is None checks.
• Adds hashing to ClusterNode and small socket read fix.
• Adds extensive new tests and proxy helpers, plus docker-compose entries for a RESP proxy test setup.

Technical Notes: The OSS SMIGRATED handler triggers a CLUSTER SLOTS-based reinitialization (optionally seeded with destination nodes) and marks affected connections for reconnect to minimize disruption.

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Review completed. 5 suggestions posted.

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