This class would belong more appropriately within the 'user' API
(core_user) instead of within the 'core' API, since it is
directly related to user data.
Since the class has only just been added to Moodle, now is a good
time to move it.
The purpose of this external function is to provide data for
asynchronous user selectors and similar widgets. It allows to search
users matching the given query in their name or other available identity
fields.
sam marshall