add
Adds an an alias for the current user. (alias, label) pairs can exist on one and only one user. If a different user already has this alias or external user id, the alias attempt will be rejected on the server (even if this method returns true).
Return
a boolean indicating whether or not the alias was successfully set.
Parameters
alias
An alias for the current user.
label
The label of the alias. Used to differentiate it from other aliases for the user.