fix(graphql): docs should answer text/html

features/graphql/docs.feature

@@ -0,0 +1,10 @@
+Feature: Documentation support
+  In order to play with GraphQL
+  As a client software developer
+  I want to reach the GraphQL documentation
+
+    Scenario: Retrieve the OpenAPI documentation
+    Given I add "Accept" header equal to "text/html"
+    And I send a "GET" request to "/graphql"
+    Then the response status code should be 200
+    And the header "Content-Type" should be equal to "text/html; charset=utf-8"

src/GraphQl/Action/GraphQlPlaygroundAction.php

@@ -37,7 +37,7 @@ public function __invoke(Request $request): Response
                 'title' => $this->title,
                 'graphql_playground_data' => ['entrypoint' => $this->router->generate('api_graphql_entrypoint')],
                 'assetPackage' => $this->assetPackage,
-            ]));
+            ]), 200, ['content-type' => 'text/html']);
         }
 
         throw new BadRequestHttpException('GraphQL Playground is not enabled.');

src/GraphQl/Action/GraphiQlAction.php

@@ -37,7 +37,7 @@ public function __invoke(Request $request): Response
                 'title' => $this->title,
                 'graphiql_data' => ['entrypoint' => $this->router->generate('api_graphql_entrypoint')],
                 'assetPackage' => $this->assetPackage,
-            ]));
+            ]), 200, ['content-type' => 'text/html']);
         }
 
         throw new BadRequestHttpException('GraphiQL is not enabled.');