A {@code User} role managed by a User Admin service.
In this context, the term "user" is not limited to just human beings. Instead, it refers to any entity that may have any number of credentials associated with it that it may use to authenticate itself.
In general, {@code User} objects are associated with a specific User Adminservice (namely the one that created them), and cannot be used with other User Admin services.
A {@code User} object may have credentials (and properties, inherited fromthe {@link Role} class) associated with it. Specific{@link UserAdminPermission} objects are required to read or change a{@code User} object's credentials.
Credentials are {@code Dictionary} objects and have semantics that aresimilar to the properties in the {@code Role} class.
@noimplement
@author $Id: 0520ec2dd4d53046fd0ea46ec685ee92a384b63b $