added releasenotes for Ditto 2.1.1

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: 2.1.1
+            url: /release_notes_211.html
+            output: web
           - title: 2.1.0
             url: /release_notes_210.html
             output: web

documentation/src/main/resources/pages/ditto/release_notes_211.md

@@ -0,0 +1,50 @@
+---
+title: Release notes 2.1.1
+tags: [release_notes]
+published: true
+keywords: release notes, announcements, changelog
+summary: "Version 2.1.1 of Eclipse Ditto, released on 28.10.2021"
+permalink: release_notes_211.html
+---
+
+This is a bugfix release, no new features since [2.1.0](release_notes_210.html) were added.
+
+## Changelog
+
+Compared to the latest release [2.1.0](release_notes_210.html), the following bugfixes were added.
+
+### Bugfixes
+
+This is a complete list of the
+[merged pull requests](https://github.com/eclipse/ditto/pulls?q=is%3Apr+milestone%3A2.1.1), including the fixed bugs.
+
+In addition, this is a complete list of the
+[merged Ditto Client pull requests](https://github.com/eclipse/ditto-clients/pulls?q=is%3Apr+milestone%3A2.1.1), including the fixed bugs.
+
+#### [Stabilize connection live status for AMQP 1.0 connections](https://github.com/eclipse/ditto/pull/1206)
+
+The connection live status was not always correct for AMQP 1.0 connections which were `misconfigured`.
+
+#### [Fixed drop behavior of mapping queue in LegacyBaseConsumerActor](https://github.com/eclipse/ditto/pull/1195)
+
+Connections using the `LegacyBaseConsumerActor` like AMQP 0.9.1, MQTT, HTTP did silently drop messages if the configured
+buffer size was reached and backpressure was applied.  
+This is now logged as warning and a retry is invoked.
+
+#### [Fix status 500 when sorting a field containing non-primitive values](https://github.com/eclipse/ditto/pull/1207)
+
+When sorting on e.g. JSON objects in the things-search a HTTP status 500 was returned.
+
+#### [Explicitly configure MongoDB query batchSize same as the limit](https://github.com/eclipse/ditto/pull/1211)
+
+The used MongoDB driver used a max `batchSize` of `16` for performing searches. When the requested result size was 
+higher than 16, this lead to multiple roundtrips/batches for a search resulting in not ideal performance.
+
+#### [Fix mqtt connection status for sources with multiple addresses](https://github.com/eclipse/ditto/pull/1214)
+
+The connection live status for MQTT connections with sources containing multiple addresses contained `failure` status
+entries for "missing" sources.
+
+#### Ditto Java Client: [Shutdown executor after stream cancellation](https://github.com/eclipse/ditto-clients/pull/174)
+
+The Ditto Java client had a thread leak which is now fixed.