Add Switch to Java 17 to ditto release notes

Signed-off-by: Yannic Klem <Yannic.Klem@bosch.io>

documentation/src/main/resources/_data/sidebars/ditto_sidebar.yml

@@ -23,6 +23,9 @@ entries:
       - title: Release Notes
         output: web
         folderitems:
+          - title: 2.4.0
+            url: /release_notes_240.html
+            output: web
           - title: 2.3.0
             url: /release_notes_230.html
             output: web

documentation/src/main/resources/pages/ditto/release_notes_240.md

@@ -0,0 +1,73 @@
+---
+title: Release notes 2.4.0
+tags: [release_notes]
+published: false
+keywords: release notes, announcements, changelog
+summary: "Version 2.4.0 of Eclipse Ditto, released on ??.??.2022"
+permalink: release_notes_240.html
+---
+
+Ditto **2.4.0** is API and [binary compatible](https://github.com/eclipse/ditto/blob/master/documentation/src/main/resources/architecture/DADR-0005-semantic-versioning.md)
+to prior Eclipse Ditto 2.x versions.
+
+## Changelog
+
+Eclipse Ditto 2.4.0 includes the following topics/enhancements:
+
+The following notable fixes are included:
+
+The following non-functional work is also included:
+
+<br/>
+
+For a complete list of all merged PRs, inspect the following milestones:
+* [merged pull requests for milestone 2.4.0](https://github.com/eclipse/ditto/pulls?q=is:pr+milestone:2.4.0)
+
+<br/>
+<br/>
+
+Compared to the latest release [2.3.0](release_notes_230.html), the following most notable changes, new features and
+bugfixes were added.
+
+### Changes
+
+#### [Upgrade to Java 17](https://github.com/eclipse/ditto/issues/1283)
+
+We upgraded the compiler target level for our service modules from 11 to 17 and also use a Java 17 runtime environment
+for our service containers. Please note that the Ditto model still remains compatible to Java 8.
+This change only affects you when you're building and deploying Ditto on your own.
+
+### New features
+
+
+### Bugfixes
+
+Several bugs in Ditto 2.2.x were fixed for 2.4.0.
+This is a complete list of the
+[merged pull requests](https://github.com/eclipse/ditto/pulls?q=is%3Apr+milestone%3A2.4.0), including the fixed bugs.
+
+
+## Migration notes
+
+Migrations required updating from Ditto 2.3.x:
+* With this release we not only switched from Java 11 to Java 17 but also from OpenJ9 to Hotspot.
+  This means that the environment variable OPENJ9_JAVA_OPTIONS needs to be renamed to JAVA_OPTIONS.
+  Make sure that all options that are defined are valid for the Hotspot JVM.
+
+## Ditto clients
+
+For a complete list of all merged client PRs, inspect the following milestones:
+* [merged pull requests for milestone 2.4.0](https://github.com/eclipse/ditto-clients/pulls?q=is:pr+milestone:2.4.0)
+
+### Ditto Java SDK
+
+No mentionable changes/enhancements/bugfixes.
+
+### Ditto JavaScript SDK
+
+See separate [Changelog](https://github.com/eclipse/ditto-clients/blob/master/javascript/CHANGELOG.md) of JS client.
+
+
+## Roadmap
+
+Looking forward, the current plans for Ditto 2.5.0 are: