UpdateMetadataRequestTopicPartition => not top level, no encoding, flexible v6+
  Topic: string // v0-v4
  Partition: int32
  ControllerEpoch: int32
  Leader: int32
  LeaderEpoch: int32
  ISR: [int32]
  ZKVersion: int32
  Replicas: [int32]
  OfflineReplicas: [int32] // v4+

// UpdateMetadataRequest is an advanced request that brokers use to
// issue metadata updates to each other.
//
// As this is an advanced request and there is little reason to issue it as a
// client, this request is undocumented.
//
// Version 1 changed the layout of the live brokers.
//
// Kafka 2.2 introduced version 5, proposed in KIP-380, which changed the
// layout of the struct to be more memory efficient.
// Kafka 3.4 introduced version 8 with KIP-866.
UpdateMetadataRequest => key 6, max version 8, flexible v6+
  ControllerID: int32
  // If KRaft controller id is used during migration. See KIP-866.
  IsKRaftController: bool // v8+
  ControllerEpoch: int32
  BrokerEpoch: int64(-1) // v5+
  PartitionStates: [UpdateMetadataRequestTopicPartition] // v0-v4
  TopicStates: [=>] // v5+
    Topic: string
    TopicID: uuid // v7+
    PartitionStates: [UpdateMetadataRequestTopicPartition]
  LiveBrokers: [=>]
    ID: int32
    Host: string // v0-v0
    Port: int32 // v0-v0
    Endpoints: [=>] // v1+
      Port: int32
      Host: string
      ListenerName: string // v3+
      SecurityProtocol: int16
    Rack: nullable-string // v2+

// UpdateMetadataResponses is returned from an UpdateMetadataRequest.
UpdateMetadataResponse =>
  ErrorCode: int16