Rails Devise Token Auth authentification without using email - ruby-on-rails

Question

I am trying to use devise_token_auth gem with API app on Rails 5.0.2.
I installed gem typically as mentioned on https://github.com/lynndylanhurley/devise_token_auth, so added to Gemfile, bundled and installed on User model. The problem is that, I don't want to use authentification (registration and login) with email. I just want to use telephone number instead (of course POST including with password and password_confirmation).
I added column :telephone_number, which will be unique to users table. And procced required steps to achieve this. https://github.com/plataformatec/devise/wiki/How-To:-Allow-users-to-sign-in-with-something-other-than-their-email-address
So this is what it looks like in code.
devise.rb
Devise.setup do |config|
...
config.authentication_keys = [ :telephone_number ]
config.case_insensitive_keys = [ :telephone_number ]
config.strip_whitespace_keys = [ :telephone_number ]
...
user.rb
class User < ActiveRecord::Base
# Include default devise modules.
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable,
:omniauthable, :authentication_keys => [:telephone_number]
include DeviseTokenAuth::Concerns::User
def email_required?
false
end
def email_changed?
false
end
application_controller.rb
class ApplicationController < ActionController::API
include DeviseTokenAuth::Concerns::SetUserByToken
before_action :configure_permitted_parameters, if: :devise_controller?
protected
def configure_permitted_parameters
added_attrs = [:telephone_number, :password, :password_confirmation, :remember_me]
devise_parameter_sanitizer.permit :sign_up, keys: added_attrs
devise_parameter_sanitizer.permit :account_update, keys: added_attrs
end
end
Server is starting properly, no exception is given. But when I test registration with RESTfull services POST on /auth it gives me validation error, that email can't be blank.
{"status":"error","data":{"id":null,"provider":"email","uid":"",
"name":null,"nickname":null,"image":null,"email":null,
"created_at":null,"updated_at":null,"telephone_number":"0123456789"},
"errors":{"email":["can't be blank","is not an email"],
"full_messages":["Email can't be blank","Email is not an email"]}}
EDIT:
Log from Puma
Started POST "/auth?=" for 127.0.0.1 at 2017-04-24 15:17:13 +0200
Processing by DeviseTokenAuth::RegistrationsController#create as */*
Parameters: {"telephone_number"=>"0123456789", "password"=>"[FILTERED]",
"password_confirmation"=>"[FILTERED]", "registration"=>{"telephone_number"=>"0123456789",
"password"=>"[FILTERED]", "password_confirmation"=>"[FILTERED]"}}
Unpermitted parameter: registration
Unpermitted parameter: registration
Unpermitted parameter: registration
(0.3ms) BEGIN
SQL (0.9ms) INSERT INTO "users" ("encrypted_password", "tokens", "created_at",
"updated_at", "telephone_number") VALUES ($1, $2, $3, $4, $5) RETURNING "id"
[["encrypted_password", "$2a$10$PgCIPAGA1VH1erHvJX5Sg.f4IPmSyfSoVM3EVbKtHkbgeUvEGL5NG"],
["tokens", "{}"], ["created_at", 2017-04-24 13:17:13 UTC], ["updated_at", 2017-04-24 13:17:13 UTC],
["telephone_number", "0123456789"]]
(0.2ms) ROLLBACK
Completed 422 Unprocessable Entity in 139ms (Views: 10.5ms | ActiveRecord: 1.3ms)
Reply on POST /auth
{"status":"error","data":{"id":null,"provider":"email","uid":"",
"name":null,"nickname":null,"image":null,"email":null,
"created_at":"2017-04-24T13:17:13.904Z","updated_at":"2017-04-24T13:17:13.904Z",
"telephone_number":"0123456789"},"errors":["An account already exists for ''"]}
It is checking and validating email, which currently is "", so no account could be registered through.
Is there any config property I should add, or override some method ?
Thank you in advance.