[DOCS] 8.5.1 Release notes

Author: picandocodigo

CHANGELOG.md

@@ -1,4 +1,12 @@
 *To see release notes for the `7.x` branch and older releases, see [CHANGELOG on the 7.17 branch](https://github.com/elastic/elasticsearch-ruby/blob/7.17/CHANGELOG.md).*
+
+## 8.5.1 Release notes
+
+### Bugfix
+
+Fixes bug when instantiating client with `api_key`: When passing in `api_key` and `transport_options` that don't include headers to the client, the `api_key` code would overwrite the arguments passed in for `transport_options`. This was fixed in [this Pull Request](https://github.com/elastic/elasticsearch-ruby/pull/1941/files).
+Thanks [svdasein](https://github.com/svdasein) for reporting in [#1940](https://github.com/elastic/elasticsearch-ruby/issues/1940).
+
 ## 8.5.0 Release notes
 
 - Tested versions of Ruby for 8.5.0: Ruby (MRI) 2.7, 3.0 and 3.1, JRuby 9.3.

docs/release_notes/85.asciidoc

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 [[release_notes_85]]
 === 8.5 Release notes
 
+[discrete]
+[[release_notes_851]]
+=== 8.5.1 Release notes
+
+[discrete]
+==== Bugfixes
+
+Fixes bug when instantiating client with `api_key`: When passing in `api_key` and `transport_options` that don't include headers to the client, the `api_key` code would overwrite the arguments passed in for `transport_options`. This was fixed in https://github.com/elastic/elasticsearch-ruby/pull/1941/files[this Pull Request].
+Thanks @svdasein for reporting in https://github.com/elastic/elasticsearch-ruby/issues/1940[#1940].
+
 [discrete]
 [[release_notes_850]]
 === 8.5.0 Release notes