Include autowire configuration for example

Newer versions of GORM do not autowire beans by default, so explicitly autowire the security service for the `beforeInsert()` example that uses it.

Author: joemccall86

docs/src/docs/asciidoc/advancedGORMFeatures/eventsAutoTimestamping.adoc

@@ -55,13 +55,19 @@ class Person {
    static constraints = {
       lastUpdatedBy nullable: true
    }
-
+   
+   static mapping = {
+      autowire true
+   }
+   
    def beforeUpdate() {
       lastUpdatedBy = securityService.currentAuthenticatedUsername()
    }
 }
 ----
 
+Notice the usage of `autowire true` above. This is required for the bean `securityService` to be injected.
+
 
 ==== The beforeDelete event
 
@@ -382,4 +388,4 @@ autoTimestampEventListener.withoutTimestamps {
 }
 ----
 
-WARNING: Because the timestamp handling is only disabled for the duration of the closure, you must flush the session during the closure execution!
+WARNING: Because the timestamp handling is only disabled for the duration of the closure, you must flush the session during the closure execution!