fix(security): request variable is only available at the resource level (#1470)

Author: alanpoulain

core/security.md

@@ -118,7 +118,7 @@ Available variables are:
 
 * `user`: the current logged in object, if any
 * `object`: the current resource, or collection of resources for collection operations
-* `request`: the current request
+* `request` (only at the resource level): the current request
 
 Access control checks in the `security` attribute are always executed before the [denormalization step](serialization.md).
 It means than for `PUT` or `PATCH` requests, `object` doesn't contain the value submitted by the user, but values currently stored in [the persistence layer](data-persisters.md).