BootCallback

A callback interface that ChannelIO.boot() notifies its result to.

Parameter	Type	Description
bootStatus	`@NonNull` BootStatus	A result of `boot()`.
user	`@Nullable` User	An instance of current user. `null` if boot has failed.

UserUpdateCallback

A callback interface that is notified when the user information is updated. Usage is the following:

Parameter	Type	Description
e	`@Nullable` Exception	An exception raised during a user update. `null` if the update was successful.
user	`@Nullable` User	An updated user instance. `null` if the update failed.