support KIP-778

This is a protocol only upgrade for a library.

README.md

@@ -341,6 +341,7 @@ generation.
 | [KIP-730](https://cwiki.apache.org/confluence/display/KAFKA/KIP-730%3A+Producer+ID+generation+in+KRaft+mode) - AllocateProducerIDs | 3.0 | Supported |
 | [KIP-734](https://cwiki.apache.org/confluence/display/KAFKA/KIP-734:+Improve+AdminClient.listOffsets+to+return+timestamp+and+offset+for+the+record+with+the+largest+timestamp) — Support MaxTimestamp in ListOffsets | 3.0 | Supported (simple version bump) |
 | [KIP-735](https://cwiki.apache.org/confluence/display/KAFKA/KIP-735%3A+Increase+default+consumer+session+timeout) — Bump default session timeout | ? | Supported |
+| [KIP-778](https://wiki.apache.org/confluence/pages/viewpage.action?pageId=188746840) — KRaft Upgrades (protocol changes only) | 3.2 | Supported |
 | [KIP-784](https://cwiki.apache.org/confluence/display/KAFKA/KIP-784%3A+Add+top-level+error+code+field+to+DescribeLogDirsResponse) — Add ErrorCode to DescribeLogDirs response| 3.1 | Supported |
 | [KIP-800](https://cwiki.apache.org/confluence/display/KAFKA/KIP-800%3A+Add+reason+to+JoinGroupRequest+and+LeaveGroupRequest) — Reason in Join/Leave group | 3.1 | Supported |
 | [KIP-814](https://cwiki.apache.org/confluence/display/KAFKA/KIP-814%3A+Static+membership+protocol+should+let+the+leader+skip+assignment) — SkipAssignment for static group leaders | 3.1 | Supported |

generate/definitions/57_update_features

@@ -1,5 +1,5 @@
 // From KIP-584 and introduced in 2.7.0, this request updates broker-wide features.
-UpdateFeaturesRequest => key 57, max version 0, flexible v0+, admin
+UpdateFeaturesRequest => key 57, max version 1, flexible v0+, admin
   TimeoutMillis(60000)
   // The list of updates to finalized features.
   FeatureUpdates: [=>]
@@ -13,7 +13,16 @@ UpdateFeaturesRequest => key 57, max version 0, flexible v0+, admin
     // downgraded/deleted. The downgrade request will fail if the new maximum
     // version level is a value that's not lower than the existing maximum
     // finalized version level.
-    AllowDowngrade: bool
+    //
+    // Replaced in v1 with ValidateOnly.
+    AllowDowngrade: bool // v0-v0
+    // Determine which type of upgrade will be performed: 1 will perform an
+    // upgrade only (default), 2 is safe downgrades only (lossless), 3 is
+    // unsafe downgrades (lossy).
+    UpgradeType: int8 // v1+
+  // True if we should validate the request, but not perform the upgrade or
+  // downgrade.
+  ValidateOnly: bool // v1+
 
 UpdateFeaturesResponse =>
   ThrottleMillis