Add Elasticsearch 7 client in Elasticsearch 8 compatibility mode

Author: alexander-schranz

.github/workflows/test-application.yaml

@@ -84,6 +84,16 @@ jobs:
                       php-cs-fixer: false
                       max-phpunit-version: '8'
 
+                    - php-version: '8.4'
+                      elasticsearch-version: '8.14.3'
+                      elasticsearch-package-constraint: '~7.17.0'
+                      minimum-stability: 'dev'
+                      dependency-versions: 'highest'
+                      tools: 'composer:v2'
+                      php-cs-fixer: false
+                      max-phpunit-version: '8'
+                      composer-options: '--ignore-platform-reqs'
+
         services:
             elasticsearch:
                 image: elasticsearch:${{ matrix.elasticsearch-version }}
@@ -114,6 +124,7 @@ jobs:
               uses: ramsey/composer-install@v1
               with:
                   dependency-versions: ${{matrix.dependency-versions}}
+                  composer-versions: ${{matrix.composer-options}}
 
             - name: Run php-cs-fixer
               if: ${{ matrix.php-cs-fixer }}

Search/Adapter/ElasticSearchAdapter.php

@@ -78,6 +78,17 @@ public function __construct(Factory $factory, ElasticSearchClient $client, $vers
         $this->factory = $factory;
         $this->client = $client;
         $this->version = $version;
+
+        if (\version_compare($this->version, '7.11.0', '>=')) {
+            $client->setConnectionParams([
+                'client' => [
+                    'headers' => [
+                        'Accept' => ['application/vnd.elasticsearch+json;compatible-with=7'],
+                        'Content-Type' => ['application/vnd.elasticsearch+json;compatible-with=7'],
+                    ],
+                ],
+            ]);
+        }
     }
 
     public function index(Document $document, $indexName)