Preparing for next developer iteration, 2.3.1. (#190)

Signed-off-by: dblock <dblock@amazon.com>

CHANGELOG.md

@@ -2,6 +2,16 @@
 
 Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
+## [Unreleased]
+### Added
+### Changed
+### Deprecated
+### Removed
+### Fixed
+### Updated APIs
+### Security
+### Dependencies
+
 ## [2.3.0]
 
 ### Added
@@ -29,6 +39,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - Fixed basic authentication being overridden by connection params in `ClientBuilder` ([#160](https://github.com/opensearch-project/opensearch-php/pull/160))
 - Fixed PHP warning in `Connection::tryDeserializeError()` for some error responses ([#167](https://github.com/opensearch-project/opensearch-php/issues/167))
 
+[Unreleased]: https://github.com/opensearch-project/opensearch-php/compare/2.3.0...main
 [2.3.0]: https://github.com/opensearch-project/opensearch-php/compare/2.2.0...2.3.0
 [2.2.0]: https://github.com/opensearch-project/opensearch-php/compare/2.1.0...2.2.0
 [2.1.0]: https://github.com/opensearch-project/opensearch-php/compare/2.0.3...2.1.0

RELEASING.md

@@ -88,4 +88,4 @@ The release process is standard across repositories in this org and is run by a
 
 1. Update CHANGELOG with the version number, and make a pull request (e.g. [#184](https://github.com/opensearch-project/opensearch-php/pull/184)).
 2. Push a tag to this repository against the right commit. This triggers the [release.yml](.github/workflows/release.yml) workflow which is responsible to get approval from the maintainers in the form of comments on the GitHub issue, release the client to [packagist](https://packagist.org/packages/opensearch-project/opensearch-php) using a manual webhook, and finally publishing a [release on GitHub](https://github.com/opensearch-project/opensearch-php/releases).
-3. Increment the version in [Client.php](https://github.com/opensearch-project/opensearch-php/blob/main/src/OpenSearch/Client.php#L55) for the next developer iteration, add an `[Unreleased]` section to [CHANGELOG](CHANGELOG.md), and make a pull request.
+3. Increment the version in [Client.php](https://github.com/opensearch-project/opensearch-php/blob/main/src/OpenSearch/Client.php#L55) for the next developer iteration, add an `[Unreleased]` section to [CHANGELOG](CHANGELOG.md), and make a pull request (e.g. [#190](https://github.com/opensearch-project/opensearch-php/pull/190)).

src/OpenSearch/Client.php

@@ -52,7 +52,7 @@ class Client
     /**
      * @deprecated since version is pulled from InstalledVersions::getVersion('opensearch-project/opensearch-php')
      */
-    public const VERSION = '2.3.0';
+    public const VERSION = '2.3.1';
 
     /**
      * @var Transport