When adding new commands or modifying commands,

Metadata or ApiVersions
=======================

Metadata modifications may need some new field copying in fetchMetadata.

ApiVersions is slightly special cased in shardedRequest, and thus may need some
modifying as well (but this is unlikely).

Admin Requests
===============

Audit if the parseErr in handleAdminReq needs to be modified.


Group / Txn Requests
====================

If the request is shardable, continue below.

Otherwise, audit if the parseErr in handleCoordinatorReq needs to be modified.

Shardable Requests
==================

If the request is an existing request, audit if any struct copying portion
needs to have new fields copied. This is especially relevant while sharding and
merging.

As well, audit if any onResp needs to do any additional cleanup.

Current shardable requests:
 - *kmsg.ListOffsetsRequest,             // key 2
 - *kmsg.DescribeGroupsRequest,          // key 15
 - *kmsg.ListGroupsRequest,              // key 16
 - *kmsg.DeleteRecordsRequest,           // key 21
 - *kmsg.OffsetForLeaderEpochRequest,    // key 23
 - *kmsg.DescribeConfigsRequest,         // key 32
 - *kmsg.AlterConfigsRequest,            // key 33
 - *kmsg.AlterReplicaLogDirsRequest,     // key 34
 - *kmsg.DescribeLogDirsRequest,         // key 35
 - *kmsg.DeleteGroupsRequest,            // key 42
 - *kmsg.IncrementalAlterConfigsRequest: // key 44