title: RubyCAS register new users, how to do it, using Devise?
body: <p><br/>
  I am struggling to register users in rubyCAS-server DB<br/> 
  I am using Devise(3.2.2) and devise_cas_authenticatable(1.3.4) as a SSO solution. Using rubyCAS as the server SSO.<br/>
  I am able to login fine, but my issue is how to register new users.
  I want to have two apps that share the same user base, intead of having the users to register in both sides.<br/>
  But it will be them to go to the website and sign_up.
  I would like to use devise because of the built-in and well tested recovery mechanisms, etc.</p>
  
  <pre><code>class User &lt; ActiveRecord::Base
      devise :cas_authenticatable, :registerable, :recoverable, :rememberable, :trackable
  end
  </code></pre>
  
  <p>After I hit the sign_up button, an error shows on the POST:<BR/></p>
  
  <pre><code>ActiveRecord::UnknownAttributeError in Devise::RegistrationsController#create
  unknown attribute: password
  </code></pre>
  
  <p>If I use database_authenticatable it works fine, so I belive Devise is well configured.
  I also have in Devise.config initializer: </p>
  
  <pre><code>config.cas_create_user = true
  </code></pre>
  
  <p>I can't find information about registering users on the SSO system. I believe it is the application job to create the users that will be shared among the apps, and I though this should work... am I right?<br/>
  If not, what would you suggest for this kind of shared users system?</p>
  
  <p>Thank you so much for your help and any suggestions you kindly provide.<br/>
  Best regards,<br/>
  Nuno</p>