/// <summary>
 /// Instantiate from an IIdentity.
 /// </summary>
 /// <remarks>
 /// The Roles for this principal will follow 
 /// those set by the Roles property, regardless of the 
 /// Identity or Authentication Type.
 /// </remarks>
 /// <param name="id">Value for user name</param>
 public UserPrincipal(IIdentity id)
 {
     Identity = new UserIdentity(id); // FIXME: Spring?
 }
 /// <summary>
 /// Instantiate default NexusPrincipal with empty NexusIdentity.
 /// </summary>
 public UserPrincipal()
 {
     Identity = new UserIdentity(); // FIXME: Spring?
 }