title: Rails session_store key change
body: <p>I need to preserve the user sessions even after I deploy a change on the session_store key:</p>
  
  <p>Before deployment:</p>
  
  <p><code>MyApp::Application.config.session_store :active_record_store, key: '_abc_session'</code></p>
  
  <p>After deployment: </p>
  
  <p><code>MyApp::Application.config.session_store :active_record_store, key: '_xyz_session'</code></p>
  
  <p>Users should still be able to use the old <code>key</code> even after this change is made.</p>
  
  <p>Any idea about how to make the <strong>old</strong> key valid even after the deployment?</p>