Adds an an alias for the 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.
Parameters
alias: string
An identifier for this user.
label: string
A label for the alias. e.g. the source of the alias, like "internal_id"
Returns Promise<boolean|undefined>
Resolves to a boolean that indicates whether the update was successfully enqueued. Resolves to undefined
if the SDK is not initialized.
Adds an an alias for the 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.