code: @JsonIgnore
  	public String getUsername() {
  		if (App.isRoot(user.getAppid())) {
  			return user.getIdentifier();
  		} else {
  			return user.getAppid() + "/" + user.getIdentifier();
  		}
  	}
docs: The username. Same as {@link User#getIdentifier()}
  @return {@link User#getIdentifier()} if user.appid == root appid, or "appid/user.identifier" if child app,
  @see User#getIdentifier()