With autoconfigure functions we don't have to do anything to inject tagged services into a collector using interfaces to define tags. But if we need some order we have to use priority, the problem is that priority only can be set by configuration file when it is a simple value.
With this change you could instead of put 0 by defualt take a look if the static method `getDefaultPriority` exists in the service class and return its default value for the service.

Example:

    <?php
    namespace App;
    use App\ServiceTagged;
    class Service implement ServiceTagged
    {
        public static function getDefaultPriority(): int
        {
            return 50; //This will be the default priority if it's not defined in a configuration file
        }
    }
    ?>

It looks like `YamlFileLoader` makes `index_by` mandatory when you define the tagged service using `arguments: [!tagged { tag: 'app.handler'}]` syntax. It's needed to accept others parameters like the new `default_priority_method` without specify `index_by` and the `XmlFielLoader` seems to accept it.

Co-Authored-By: Valentin Udaltsov <[email protected]>

Co-Authored-By: Kevin Verschaeve <[email protected]>