openapi: new Operation(
                summary: 'Retrieves a user avatar',
                description: 'Retrieves the PNG image corresponding to a user avatar',
                responses: [
                    '200' => [
                        'description' => 'The user avatar',
                        'content' => [
                            'image/png' => [
                                'schema' => [
                                    'type' => 'string',
                                    'format' => 'binary',
                                ],
                            ],
                        ],
                    ],
                    '404' => [
                        'description' => 'User does not exist',
                    ],
                ],
            ),