[Contracts][DependencyInjection] Add ServiceCollectionInterface

Author: alexandre-daubois

service_container/service_subscribers_locators.rst

@@ -111,17 +111,30 @@ in the service subscriber::
     can also manually add the ``container.service_subscriber`` tag.
 
 The injected service is an instance of :class:`Symfony\\Component\\DependencyInjection\\ServiceLocator`
-which implements both the PSR-11 ``ContainerInterface`` and :class:`Symfony\\Contracts\\Service\\ServiceProviderInterface`.
-It is also a callable and a countable::
+which implements the PSR-11 ``ContainerInterface``, the
+:class:`Symfony\\Contracts\\Service\\ServiceProviderInterface` and the
+:class:`Symfony\\Contracts\\Service\\ServiceCollectionInterface`. Because of
+this, the locator is callable, countable and traversable::
 
     // ...
     $numberOfHandlers = count($this->locator);
     $nameOfHandlers = array_keys($this->locator->getProvidedServices());
+
+    // you can iterate through all services of the locator
+    foreach ($this->locator as $serviceId => $service) {
+        // do something with the service, the service id or both
+    }
+
     // ...
     $handler = ($this->locator)($commandClass);
 
     return $handler->handle($command);
 
+.. versionadded:: 7.1
+
+    The :class:`Symfony\\Contracts\\Service\\ServiceCollectionInterface`
+    was introduced in Symfony 7.1.
+
 Including Services
 ------------------