code: @SuppressWarnings("WeakerAccess")
      public AuthenticationRequest loginWithEmail(@NonNull String email, @NonNull String verificationCode) {
          return loginWithEmail(email, verificationCode, EMAIL_CONNECTION);
      }
docs: Log in a user using an email and a verification code received via Email (Part of passwordless login flow)
  By default it will try to authenticate using the "email" connection.
  Example usage:
  <pre>
  {@code
  client.loginWithEmail("{email}", "{code}")
  .start(new BaseCallback<Credentials>() {
  {@literal}Override
  public void onSuccess(Credentials payload) { }
  
  {@literal}@Override
  public void onFailure(AuthenticationException error) { }
  });
  }
  </pre>
  
  @param email            where the user received the verification code
  @param verificationCode sent by Auth0 via Email
  @return a request to configure and start that will yield {@link Credentials}