title: Redmine: 422 invalid form authenticity token
body: <p>I'm using <a href="https://github.com/chrodriguez/redmine_omniauth_saml" rel="noreferrer">this</a> plugin to enable SSO between my IDP and redmine. Purpose is to avoid re entering username and password when login to the redmine. Both Redmine and the IDP connected to an external LDAP. Problem is after redirecting back to the redmine from my IDP (after entering username &amp; password), It's giving this error.</p>
  
  <p>Redmine version: 2.5.2,
  Ruby version: 1.9.3,
  Rails version: 3.2.19</p>
  
  <p><img src="https://i.stack.imgur.com/CePVS.png" alt="error"></p>