feature #28947 [Messenger] remove classifying sub-namespaces in favor of semantic ones (nicolas-grekas)

This PR was merged into the 4.2-dev branch.

Discussion
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[Messenger] remove classifying sub-namespaces in favor of semantic ones

| Q             | A
| ------------- | ---
| Branch?       | 4.2
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

While working on the component, I found it hard to discover the meaning of the `Asynchronous` and `Enhancers` sub-namespaces. Now that I know the component better, I understand they're only classifying namespaces with no specific technical semantics.

I'd like to remove them to make the component easier to discover.
This PR introduces a few new semantic sub-namespaces instead.

From the changelog:
  * Classes in the `Middleware\Enhancers` sub-namespace have been moved to the `Middleware` one
 * Classes in the `Asynchronous\Routing` sub-namespace have been moved to the `Transport\Sender\Locator` sub-namespace
 * The `Asynchronous/Middleware/SendMessageMiddleware` class has been moved to the `Middleware` namespace
 * `SenderInterface` and `ChainSender` classes have been moved to the `Transport\Sender` sub-namespace
 * `ReceiverInterface` and its implementations have been moved to the `Transport\Receiver` sub-namespace

Commits
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16afb5e2b4 [Messenger] remove classifying sub-namespaces in favor of semantic ones

Author: sroze

DependencyInjection/FrameworkExtension.php

@@ -68,7 +68,7 @@
 use Symfony\Component\Messenger\Handler\MessageHandlerInterface;
 use Symfony\Component\Messenger\MessageBus;
 use Symfony\Component\Messenger\MessageBusInterface;
-use Symfony\Component\Messenger\Transport\ChainSender;
+use Symfony\Component\Messenger\Transport\Sender\ChainSender;
 use Symfony\Component\Messenger\Transport\TransportFactoryInterface;
 use Symfony\Component\Messenger\Transport\TransportInterface;
 use Symfony\Component\PropertyAccess\PropertyAccessor;

Resources/config/messenger.xml

@@ -8,11 +8,11 @@
         <defaults public="false" />
 
         <!-- Asynchronous -->
-        <service id="messenger.asynchronous.routing.sender_locator" class="Symfony\Component\Messenger\Asynchronous\Routing\ContainerSenderLocator">
+        <service id="messenger.asynchronous.routing.sender_locator" class="Symfony\Component\Messenger\Transport\Sender\Locator\ContainerSenderLocator">
             <argument type="service" id="messenger.sender_locator" />
             <argument type="collection" /> <!-- Message to sender ID mapping -->
         </service>
-        <service id="messenger.middleware.route_messages" class="Symfony\Component\Messenger\Asynchronous\Middleware\SendMessageMiddleware">
+        <service id="messenger.middleware.route_messages" class="Symfony\Component\Messenger\Middleware\SendMessageMiddleware">
             <argument type="service" id="messenger.asynchronous.routing.sender_locator" />
             <argument type="collection" /> <!-- Message to send and handle mapping -->
         </service>