This data-source uses the Umbraco users to populate the items of a compatible editor, e.g. Data List.
The configuration of the Umbraco Users data-source has one option, to select a User Group (role) to filter the users that are listed. If left empty, then all users will be listed.
The value for the Umbraco Users data-source item is an IUser object-type. Typically, this will be a concrete class of User, (unless if you are doing advanced user group management?).
Depending on the List editor used, this may be wrapped in a List<IUser>.
