[DependencyInjection] [WIP] Allow service subscribers to return `SubscribedService[]`

[kbond]

Q	A
Branch?	6.2
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	n/a
License	MIT
Doc PR	todo

This allows ServiceSubscriberInterface::getSubscribedServices() to return SubscribedService[] which now has the ability to add DI attribute objects (ie Target).

public static function getSubscribedServices(): array
{
    return [
        new SubscribedService('logger', Psr\Log\LoggerInterface::class),
        new SubscribedService(type: Psr\Log\LoggerInterface::class, nullable: true),
        new SubscribedService('http_client', HttpClientInterface::class, attributes: new Target('githubApi'))),
    ];
}

When using the ServiceSubscriberTrait, the SubscribedService attribute can add attributes as well:

#[SubscribedService(attributes: new Target('githubApi'))]
private function httpClient(): ?HttpClientInterface
{
    return $this->container->get(__METHOD__);
}

TODO:

• [ ] Implementation
• [ ] Tests
• [ ] Changelog

[nicolas-grekas]

I like it :) Let's see how DI can leverage that for Autowiring now.

[fabpot]

Thank you @kbond.