title: ArgumentError: After create callback :send_on_create_confirmation_instructions has not been defined. devise_token_auth
body: <p>I'm using <a href="https://github.com/lynndylanhurley/devise_token_auth" rel="nofollow">devise_token_auth</a> for authenticating a rails-api application. I have included these devise modules in my user model as shown below.</p>
  
  <pre><code>class User &lt; ActiveRecord::Base
    devise :database_authenticatable, :registerable,
           :recoverable, :rememberable, :trackable, :confirmable
  end
  </code></pre>
  
  <p>The problem is when i do a <code>POST</code> request on the email registration endpoint, <code>http://localhost:3000/auth</code> with <code>email</code>, <code>password</code> and <code>password_confirmation</code> as params. It only succeeds once after a server restart. All subsequent requests to register an user fail with this error:</p>
  
  <pre><code>{
    "status": 500,
    "error": "Internal Server Error",
    "exception": "#&lt;ArgumentError: After create callback     :send_on_create_confirmation_instructions has not been defined&gt;",
    "traces": {
           ...
     }
  </code></pre>
  
  <p>This means I have to restart the server every time I want to register a user.</p>
  
  <p>This is what I have in the <code>Gemfile</code>.</p>
  
  <pre><code>gem 'devise', github: "plataformatec/devise"
  gem 'devise_token_auth', github: "lynndylanhurley/devise_token_auth"
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>When I make any change in <code>ApplicationController</code> and save it. The request succeeds without restarting the server.</p>