< Client's hostname
< Client's \p client.id
< Member assignment (binary), * format depends on \p protocol_type.
< Member assignment size in bytes
< Member id (generated by broker)
< Member metadata (binary), * format depends on \p protocol_type.
< Member metadata size in bytes
@brief Group member information
For more information on \p member_metadata format, see https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-GroupMembershipAPI