[docs] Release notes for 9.0.0

docs/release-notes/breaking-changes.md

@@ -16,7 +16,9 @@ Breaking changes can impact your Elastic applications, potentially disrupting no
 % **Action**<br> Steps for mitigating deprecation impact.
 % ::::
 
-% ## 9.0.0 [elasticsearch-php-client-900-breaking-changes]
+## 9.0.0 [elasticsearch-php-client-900-breaking-changes]
+
+_No breaking changes_
 
 % ::::{dropdown} Title of breaking change
 % Description of the breaking change.

docs/release-notes/deprecations.md

@@ -16,7 +16,9 @@ Review the deprecated functionality for Elasticsearch PHP Client. While deprecat
 % **Action**<br> Steps for mitigating deprecation impact.
 % ::::
 
-% ## 9.0.0 [elasticsearch-php-client-900-deprecations]
+## 9.0.0 [elasticsearch-php-client-900-deprecations]
+
+_No deprecations_
 
 % Description of the deprecation and steps to update implementation.
 % For more information, check [PR #](PR link).

docs/release-notes/index.md

@@ -24,4 +24,12 @@ To check for security updates, go to [Security announcements for the Elastic sta
 
 ### Features and enhancements [elasticsearch-php-client-900-features-enhancements]
 
-### Fixes [elasticsearch-php-client-900-fixes]
+- **Compatibility with Elasticsearch 9.0:** All changes and additions to Elasticsearch APIs for its 9.0 release are reflected in this release.
+- **Serverless client merged in:** the `elastic/elasticsearch-serverless` client is being deprecated, and its functionality has been merged back into this client. This should have zero impact on the way the client works by default. If an ednpoint is available in serverless, the PHP function will contains a `@group serverless` phpdoc attribute.
+If you try to use an endpoint that is not available in serverless you will get a `410` HTTP error with a message as follows:
+"this endpoint exists but is not available when running in serverless mode".
+- **New transport library with PSR-18 cURL client as default:** we've removed the Guzzle dependency from the client. By default, the built-in cURL-based HTTP client will be used if no other PSR-18 compatible clients are detected. See release [9.0.0](https://github.com/elastic/elastic-transport-php/releases/tag/v9.0.0) of elastic-transport-php.
+
+### Fixes [elasticsearch-php-client-900-fixes]
+
+- **Fixed PHPStan array shape:** we fixed the array shape definition for all the endpoints, upgrading PHPStan to verion 2.1. See PR [#1439](https://github.com/elastic/elasticsearch-php/pull/1439)

docs/release-notes/known-issues.md

@@ -5,6 +5,10 @@ navigation_title: "Known issues"
 
 # Elasticsearch PHP Client known issues [elasticsearch-php-client-known-issues]
 
+## 9.0.0 
+
+_No known issues_
+
 % Use the following template to add entries to this page.
 
 % :::{dropdown} Title of known issue