feature #9477 Removing warning about bind + controller + scalar values (weaverryan)

This PR was squashed before being merged into the master branch (closes #9477).

Discussion
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Removing warning about bind + controller + scalar values

Docs for symfony/symfony#26658 :)

Commits
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af00dbc adding version note about scalar bind args
4312518 Removing warning about bind + controller + scalar values

Author: weaverryan

controller.rst

@@ -241,6 +241,8 @@ the argument by its name:
                 bind:
                     # for any $logger argument, pass this specific service
                     $logger: '@monolog.logger.doctrine'
+                    # for any $projectDir argument, pass this parameter value
+                    $projectDir: '%kernel.project_dir%'
 
     .. code-block:: xml
 
@@ -260,6 +262,7 @@ the argument by its name:
                         type="service"
                         id="monolog.logger.doctrine"
                     />
+                    <bind key="$projectDir">%kernel.project_dir%</bind>
                 </service>
             </services>
         </container>
@@ -274,19 +277,16 @@ the argument by its name:
             ->setPublic(true)
             ->setBindings(array(
                 '$logger' => new Reference('monolog.logger.doctrine'),
+                '$projectDir' => '%kernel.project_dir%'
             ))
         ;
 
 You can of course also use normal :ref:`constructor injection <services-constructor-injection>`
 in your controllers.
 
-.. caution::
-
-    You can *only* pass *services* to your controller arguments in this way. It's not
-    possible, for example, to pass a service parameter as a controller argument,
-    even by using ``bind``. If you need a parameter, use the ``$this->getParameter('kernel.debug')``
-    shortcut or pass the value through your controller's ``__construct()`` method
-    and specify its value with ``bind``.
+.. versionadded:: 4.1
+    The ability to bind scalar values to controller arguments was introduced in
+    Symfony 4.1. Previously you could only bind services.
 
 For more information about services, see the :doc:`/service_container` article.