added release notes for Ditto 3.1.1

Signed-off-by: Thomas Jaeckle <thomas.jaeckle@bosch.io>

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

@@ -23,6 +23,9 @@ entries:
       - title: Release Notes
         output: web
         folderitems:
+          - title: 3.1.1
+            url: /release_notes_311.html
+            output: web
           - title: 3.1.0
             url: /release_notes_310.html
             output: web

documentation/src/main/resources/pages/ditto/release_notes_311.md

@@ -0,0 +1,37 @@
+---
+title: Release notes 3.1.1
+tags: [release_notes]
+published: true
+keywords: release notes, announcements, changelog
+summary: "Version 3.1.1 of Eclipse Ditto, released on 05.01.2023"
+permalink: release_notes_311.html
+---
+
+This is a bugfix release, no new features since [3.0.0](release_notes_300.html) were added.
+
+## Changelog
+
+Compared to the latest release [3.0.0](release_notes_300.html), the following bugfixes were added.
+
+### Bugfixes
+
+This is a complete list of the
+[merged pull requests](https://github.com/eclipse-ditto/ditto/pulls?q=is%3Apr+milestone%3A3.1.1).
+
+#### [Revert client actors from cluster sharding to router pool](https://github.com/eclipse-ditto/ditto/pull/1560)
+
+In Ditto 3.1.0, a connection's `clientCount` greater than 1 did no longer guarantee that clients run on different 
+connectivity services which could have scalability effects, e.g. regarding throttling.  
+E.g. a connection with 5 clients in a cluster of 5 Ditto connectivity services could in the worst case have led to the 
+situation that all 5 clients run on the same connectivity service.
+
+This was fixed by undoing the in 3.1.0 added "cluster sharding" for connectivity clients.
+
+
+### Bugfixes Ditto Java client
+
+#### [Add options for live message conditions](https://github.com/eclipse-ditto/ditto-clients/pull/210)
+
+For the Ditto Java client version 3.1.0 merging the client options for sending messages conditionally was forgotten
+to be merged.  
+The 3.1.1 client includes this new functionality.