MINOR: add KafkaStreams 4.0 information to top-level upgrade section (#18543)

Reviewers: Bruno Cadonna <[email protected]>, Alieh Saeedi <[email protected]>

Author: mjsax

docs/streams/upgrade-guide.html

@@ -144,7 +144,7 @@ <h3><a id="streams_api_changes_400" href="#streams_api_changes_400">Streams API
     <p>
         In this release, eos-v1 (Exactly Once Semantics version 1) is no longer supported. To use eos-v2, brokers must be running version 2.5 or later.
         Additionally, all deprecated methods, classes, APIs, and config parameters up to and including AK 3.5 release have been removed.
-        A few important ones are listed below. The full list can be found <a href="https://issues.apache.org/jira/browse/KAFKA-12822">here</a>.
+        A few important ones are listed below. The full list can be found in <a href="https://issues.apache.org/jira/browse/KAFKA-12822">KAFKA-12822</a>.
         <ul>
             <li><a href="https://issues.apache.org/jira/browse/KAFKA-12829">Old processor APIs</a></li>
             <li><a href="https://issues.apache.org/jira/browse/KAFKA-12823">KStream#through() in both Java and Scala</a></li>

docs/upgrade.html

@@ -23,9 +23,10 @@ <h4><a id="upgrade_4_0_0" href="#upgrade_4_0_0">Upgrading to 4.0.0 from any vers
     <h5><a id="upgrade_400_notable" href="#upgrade_400_notable">Notable changes in 4.0.0</a></h5>
     <ul>
         <li>
-            Old protocol API versions have been removed. Users should ensure brokers are version 2.1 or higher before upgrading the Java clients to 4.0.
-            Similarly, users should ensure their Java clients version 2.1 or higher before upgrading the brokers to 4.0. Finally, care also needs to be
-            taken when it comes to kafka clients that are not part of Apache Kafka, please see
+            Old protocol API versions have been removed. Users should ensure brokers are version 2.1 or higher before upgrading the Java clients
+	    (including Connect and Kafka Streams which use the clients internally) to 4.0.
+            Similarly, users should ensure their Java clients (including Connect and Kafka Streams) version is 2.1 or higher before upgrading the brokers to 4.0.
+	    Finally, care also needs to be taken when it comes to kafka clients that are not part of Apache Kafka, please see
             <a href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-896%3A+Remove+old+client+protocol+API+versions+in+Kafka+4.0">KIP-896</a> for the details.
         </li>
         <li>A number of deprecated classes, methods, configurations and tools have been removed.
@@ -248,12 +249,26 @@ <h5><a id="upgrade_400_notable" href="#upgrade_400_notable">Notable changes in 4
                         </li>
                     </ul>
                 </li>
+                <li><b>Kafka Streams</b>
+                    <ul>
+                        <li>
+			    All public API, deprecated in Apache Kafka 3.6 or an earlier release, have been removed, with the exception of <code>JoinWindows.of()</code> and <code>JoinWindows#grace()</code>.
+			    See <a href="https://issues.apache.org/jira/browse/KAFKA-17531">KAFKA-17531</a> for details.
+                        </li>
+                        <li>
+			    The most important changes are highlighted in the <a href=""/{{version}}/documentation/streams/upgrade-guide.html#streams_api_changes_400">Kafka Streams upgrade guide</a>.
+                        </li>
+                        <li>
+			    For a full list of changes, see <a href="https://issues.apache.org/jira/browse/KAFKA-12822">KAFKA-12822</a>.
+                        </li>
+                    </ul>
+                </li>
             </ul>
         </li>
         <li>Other changes:
             <ul>
                 <li>
-                    The minimum Java version required by clients and streams applications has been increased from Java 8 to Java 11
+                    The minimum Java version required by clients and Kafka Streams applications has been increased from Java 8 to Java 11
                     while brokers, connect and tools now require Java 17.
                     See <a href="https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=181308223">KIP-750</a> and
                     <a href="https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=284789510">KIP-1013</a> for more details.
@@ -290,6 +305,11 @@ <h5><a id="upgrade_400_notable" href="#upgrade_400_notable">Notable changes in 4
                     been updated to enable the replication of topics that appear to be internal but aren't truly internal to Kafka and Mirror Maker 2.
                     See <a href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-1074%3A+Allow+the+replication+of+user+internal+topics">KIP-1074</a> for more details.
                 </li>
+                <li>
+                    KIP-714 is now enabled for Kafka Streams via <a href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-1076%3A++Metrics+for+client+applications+KIP-714+extension">KIP-1076</a>.
+		    This allows to not only collect the metric of the internally used clients of a Kafka Streams appliction via a broker-side plugin,
+		    but also to collect the <a href="/{{version}}/documentation/#kafka_streams_monitoring">metrics</a> of the Kafka Streams runtime itself.
+                </li>
             </ul>
         </li>
     </ul>