code: public Task<Void> registerWithEmail(@NonNull final String email, @NonNull final String password) {
      return dispatcher.dispatchTask(
          new Callable<Void>() {
            @Override
            public Void call() {
              registerWithEmailInternal(email, password);
              return null;
            }
          });
    }
docs: Registers a new user with the given email and password.
  
  @param email the email to register with. This will be the username used during log in.
  @param password the password to associated with the email. The password must be between
  6 and 128 characters long.
  @return A {@link Task} that completes when registration completes/fails.