MINOR: Mark streams RPCs as unstable (#19292)

Streams groups RPCs are not enabled by default, but they should also be
marked as unstable.

Reviewers: Bruno Cadonna <cadonna@apache.org>

Author: lucasbru

clients/src/main/java/org/apache/kafka/clients/consumer/internals/StreamsGroupHeartbeatRequestManager.java

@@ -476,7 +476,7 @@ private NetworkClientDelegate.UnsentRequest makeHeartbeatRequestAndHandleRespons
 
     private NetworkClientDelegate.UnsentRequest makeHeartbeatRequest(final long currentTimeMs) {
         NetworkClientDelegate.UnsentRequest request = new NetworkClientDelegate.UnsentRequest(
-            new StreamsGroupHeartbeatRequest.Builder(this.heartbeatState.buildRequestData()),
+            new StreamsGroupHeartbeatRequest.Builder(this.heartbeatState.buildRequestData(), true),
             coordinatorRequestManager.coordinator()
         );
         heartbeatRequestState.onSendAttempt(currentTimeMs);

clients/src/main/resources/common/message/StreamsGroupDescribeRequest.json

@@ -20,6 +20,10 @@
   "name": "StreamsGroupDescribeRequest",
   "validVersions": "0",
   "flexibleVersions": "0+",
+  // The StreamsGroupDescribeRequest API is added as part of KIP-1071 and is still under
+  // development. Hence, the API is not exposed by default by brokers unless
+  // explicitly enabled.
+  "latestVersionUnstable": true,
   "fields": [
     { "name": "GroupIds", "type": "[]string", "versions": "0+", "entityType": "groupId",
       "about": "The ids of the groups to describe" },

clients/src/main/resources/common/message/StreamsGroupHeartbeatRequest.json

@@ -20,6 +20,10 @@
   "name": "StreamsGroupHeartbeatRequest",
   "validVersions": "0",
   "flexibleVersions": "0+",
+  // The StreamsGroupDescribeRequest API is added as part of KIP-1071 and is still under
+  // development. Hence, the API is not exposed by default by brokers unless
+  // explicitly enabled.
+  "latestVersionUnstable": true,
   "fields": [
     { "name": "GroupId", "type": "string", "versions": "0+", "entityType": "groupId",
       "about": "The group identifier." },

core/src/test/scala/unit/kafka/server/KafkaApisTest.scala

@@ -9652,7 +9652,7 @@ class KafkaApisTest extends Logging {
   def testStreamsGroupHeartbeatReturnsUnsupportedVersion(): Unit = {
     val streamsGroupHeartbeatRequest = new StreamsGroupHeartbeatRequestData().setGroupId("group")
 
-    val requestChannelRequest = buildRequest(new StreamsGroupHeartbeatRequest.Builder(streamsGroupHeartbeatRequest).build())
+    val requestChannelRequest = buildRequest(new StreamsGroupHeartbeatRequest.Builder(streamsGroupHeartbeatRequest, true).build())
     metadataCache = {
       val cache = new KRaftMetadataCache(brokerId, () => KRaftVersion.KRAFT_VERSION_1)
       val delta = new MetadataDelta(MetadataImage.EMPTY);