Rails engine with --full option model

I tried to separate my model as a rails engine, to use that in more then one application.

In order to achieve this I created rails plugin new engine_name --full so that I can use all the routes and models without mounting in an isolated namespace.

   class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  scope :find_user, ->(id) { where(id: id)}

  def self.say_hello(str)
    puts "Welcome #{str}"
  end
end

the above is my plugin without module encapsulated (because it created with --full)

I can successfully include this into any rails app and can access the route and create user.

also I'm able to access class methods from the model using

2.1.5 :015 > User.say_hello("ferdy")
Welcome ferdy

when I try to access the model using

User.create(email:"ferdsfd@sdfds.com",password:12345678)
ActiveRecord::StatementInvalid: Could not find table 'users'

what would be the problem? could any one help how to access plugin model?