Release notes for 9.0.8 (#18247)

* Update release notes for 9.0.8

* finalize release notes

* Update docs/release-notes/index.md

Co-authored-by: Karen Metts <[email protected]>

---------

Co-authored-by: logstashmachine <[email protected]>
Co-authored-by: donoghuc <[email protected]>
Co-authored-by: Karen Metts <[email protected]>

Author: 4 people

docs/release-notes/index.md

@@ -21,6 +21,17 @@ To check for security updates, go to [Security announcements for the Elastic sta
 % ### Fixes [logstash-next-fixes]
 % *
 
+## 9.0.8 [logstash-9.0.8-release-notes]
+
+No user-facing changes in Logstash core.
+
+### Plugins [logstash-plugin-9.0.8-changes]
+
+**Elasticsearch Output - 12.0.7**
+
+* Support both, encoded and non-encoded api-key formats on plugin configuration [#1223](https://github.com/logstash-plugins/logstash-output-elasticsearch/pull/1223)
+
+
 ## 9.0.7 [logstash-9.0.7-release-notes]
 
 ### Fixes [logstash-9.0.7-fixes]