[Maintenance] Move the Stack's app related code under the app/ dire…

…ctory (#5)

Every "demo" code like custom Twig Components, controllers, etc. should
be placed under the `app/` directory.

composer.json

@@ -50,10 +50,8 @@
         }
     },
     "autoload-dev": {
-        "classmap": [
-            "src/Kernel.php"
-        ],
         "psr-4": {
+            "App\\": "app/",
             "TestApplication\\Sylius\\TwigHooks\\": "src/TwigHooks/tests/Functional/.application/src/",
             "Tests\\Sylius\\TwigHooks\\": "src/TwigHooks/tests/"
         }

config/services.yaml

@@ -1,6 +1,29 @@
+# Put parameters here that don't need to change on each machine where the app is deployed
+# https://symfony.com/doc/current/best_practices/configuration.html#application-related-configuration
 parameters:
+    locale: en_US
 
 services:
+    # Default configuration for services in *this* file
     _defaults:
-        autowire: false
-        autoconfigure: false
+        # Automatically injects dependencies in your services
+        autowire: true
+
+        # Automatically registers your services as commands, event subscribers, etc.
+        autoconfigure: true
+
+        # Allows optimizing the container by removing unused services; this also means
+        # fetching services directly from the container via $container->get() won't work
+        public: false
+
+    # Makes classes in src/ available to be used as services;
+    # this creates a service per class whose id is the fully-qualified class name
+    App\:
+        resource: '../app/*'
+        exclude: '../app/{Entity,Migrations,Tests,Kernel.php}'
+
+    # Controllers are imported separately to make sure services can be injected
+    # as action arguments even if you don't extend any base controller class
+#    App\Controller\:
+#        resource: '../src/Controller'
+#        tags: ['controller.service_arguments']