title: How to send email activation link with Heroku and Send Grid?
body: <p><strong>Errors in heroku logs when I try to send email activation link:</strong></p>
  
  <blockquote>
    <p>2018-01-17T07:37:09.783615+00:00 app[web.1]:
    [f3c128f0-83ad-4879-ae6c-a54b28030290]   [1m[35m (0.7ms)[0m 
    [1m[35mBEGIN[0m
        2018-01-17T07:37:09.891482+00:00 app[web.1]: [f3c128f0-83ad-4879-ae6c-a54b28030290] Completed 500 Internal Server
    Error in 188ms (ActiveRecord: 10.7ms)
        2018-01-17T07:37:09.892707+00:00 app[web.1]: [f3c128f0-83ad-4879-ae6c-a54b28030290]<br>
        2018-01-17T07:37:09.871499+00:00 app[web.1]: [f3c128f0-83ad-4879-ae6c-a54b28030290]   [1m[35m (1.1ms)[0m 
    [1m[31mROLLBACK[0m
        2018-01-17T07:37:09.892886+00:00 app[web.1]: [f3c128f0-83ad-4879-ae6c-a54b28030290] NoMethodError (undefined method
    activation_digest= for #
        2018-01-17T07:37:09.892887+00:00 app[web.1]: Did you mean?  activation_token=):
        2018-01-17T07:37:09.892920+00:00 app[web.1]: [f3c128f0-83ad-4879-ae6c-a54b28030290]<br>
        2018-01-17T07:37:09.892966+00:00 app[web.1]: [f3c128f0-83ad-4879-ae6c-a54b28030290] app/models/user.rb:71:in
    create_activation_digest
        2018-01-17T07:37:09.892967+00:00 app[web.1]: [f3c128f0-83ad-4879-ae6c-a54b28030290]
    app/controllers/users_controller.rb:23:in `create'
        2018-01-17T07:37:09.892966+00:00 heroku[router]: at=info method=POST path="/users" host=letsgo228.herokuapp.com
    request_id=f3c128f0-83ad-4879-ae6c-a54b28030290 fwd="61.6.75.149"
    dyno=web.1 connect=1ms service=194ms status=500 bytes=1891
    protocol=https
        2018-01-17T07:37:10.572375+00:00 heroku[router]: at=info method=GET path="/favicon.ico" host=letsgo228.herokuapp.com
    request_id=6b2a9847-7844-4ae9-a7df-e1405b86b08f fwd="61.6.75.149"
    dyno=web.1 connect=0ms service=1ms status=304 bytes=112 protocol=https</p>
  </blockquote>
  
  <p><strong>User model</strong> </p>
  
  <pre><code> # Creates and assigns the activation token and digest.
    def create_activation_digest
      self.activation_token  = User.new_token
      self.activation_digest = User.digest(activation_token)
    end
  end
  </code></pre>
  
  <p><strong>user_contrller</strong></p>
  
  <pre><code>def new
      @user = User.new
    end
  
    def create
      @user = User.new(user_params)
      if @user.save
        @user.send_activation_email
        flash[:info] = "Пожалуйста проверьте свою почту,в течении 1 минуты придет письмо для активации аккаунта"
        redirect_to root_url
      else
        render 'new'
      end
    end
  </code></pre>