document addUser() more

topics/user-storage/import.adoc

@@ -69,6 +69,11 @@ For your providers, you can use this to _intercept_ other methods on the local `
 with your extern store.  For example, get methods could make sure that the local store is in sync.   Set methods
 keep external store in sync with local one.
 
+NOTE: If your provider is implementing the `UserRegistrationProvider` interface, your `removeUser()` method does not
+      need to remove the user from local storage.  The runtime will automatically perform this operation.  Also
+      note that `removeUser()` will be invoked before it is removed from local storage.
+
+
 ==== ImportedUserValidation Interface
 
 If you remember earlier in this chapter, we discussed how querying for a user worked.  Local storage is queried first,

topics/user-storage/registration-query.adoc

@@ -56,6 +56,10 @@ Notice that when adding a user we set the password value of the property map to
 we can't have null values for a property in the property value.  We also have to modify the `CredentialInputValidator`
 methods to reflect this.
 
+`addUser()` will be called if the provider implements the `UserRegistrationProvider` interface.  If your provider has
+a configuration switch to turn of adding a user, returning `null` from this method will skip the provider and call
+the next one.
+
 .PropertyFileUserStorageProvider
 [source,java]
 ----