Make igbinary usable without needing module enabled.

MR created.

Uploading patch for easier Composer usage.

Thanks for the review!

FYI, because autoloader generation is not impacted by the patch (I guess the change should be merged to have an impact), in my project composer.json I have added the following configuration:

    "autoload": {
        ...
        "psr-4": {
            "Drupal\\igbinary\\": "app/modules/contrib/igbinary/src"
        }
    },

Of course, re-reading my sentence, it was not clear.

Currently to use Igbinary you have to enable the module because even if including manually the services.yml file in settings.php, the classes are not in the Composer autoload.

Whereas in Redis module there are psr-4 instructions in the composer.json which allow to download the module with Composer and just by including manually the services.yml file in settings.php you can use Redis without having to enable the module.

With the proposed changes, it will be possible to use Igbinary by manually including its services.yml in settings.php and use it without having to enable the module.

@SocialNicheGuru Thanks for the feedbacks.

But I have been using Redis for years, also during Drupal installation (when it is not enabled yet), without the mentionned line:

$class_loader->addPsr4('Drupal\\redis\\', 'modules/contrib/redis/src');

Since the first version of the D8+ Redis module, the following lines are present in the composer.json file of the Redis module:

"autoload": {
    "psr-4": {
      "Drupal\\redis\\": "src"
    }
  }

So when getting the Redis sources with Composer the autoload is automatic.

Those are the same lines that I want to add in the composer.json of igbinary. Otherwise until it is merged, you can change the composer.json of the project using the module with the lines from comment 4.

Maybe if you are not using Composer to download Redis then the $class_loader stuff is required but It should only be something documented. And currently in Redis it is only used in a test because I guess in the tests the sources are not handled with Composer.