add note on service parameters regarding ScopeWideningInjectionException

Author: joelclermont

book/service_container.rst

@@ -231,6 +231,15 @@ looks up the value of each parameter and uses it in the service definition.
 
         <argument type="string">http://symfony.com/?foo=%%s&bar=%%d</argument>
 
+.. note::
+
+    It can be useful to pass other services in as arguments to your custom service.
+    For example, you may want to pass in the `request` service as an argument.
+    In these cases, you may receive a `ScopeWideningInjectionException`.
+    To understand this problem better and learn how to solve it, refer to
+    the cookbook article :doc:`/cookbook/service_container/scopes` for a
+    few solutions.
+
 The purpose of parameters is to feed information into services. Of course
 there was nothing wrong with defining the service without using any parameters.
 Parameters, however, have several advantages: