title: Oauth2 and user (not) logout
body: <p>We have a setup with 3 components</p>
  <ol>
  <li>A Dashboard/Portal for the user to manage things</li>
  <li>A Moodle instance for elearning courses</li>
  <li>A Keycloak server for SSO</li>
  </ol>
  <p>When the user accesses the portal, it is redirected to Keycloak to sign in and is afterward returned to the dashboard.
  From the dashboard the user can jump to moodle, and moodle check's the login state, if not logged in it asks Keycloak for the user login and uses the already logged in user.</p>
  <p>This works fine and as expected.</p>
  <p>But we have a problem, when a user logs out and another user logs in:</p>
  <ol>
  <li>User 1 does login via Dashboard/Keycloak and the goes to Moodle, which recognizes User 1</li>
  <li>User 1 closes the Moodle window and returns to the dashboard</li>
  <li>In the dahboard user 1 logs out and user 2 logs in via Keycloak too
  And here comes the problem:</li>
  <li>User 2 goes from the dashboard to Moodle, here Moodle still is logged in as User 1...</li>
  </ol>
  <p>If the user does a logout in Moodle itself in step 2, then in step 4 user 2 is active and everything is ok.</p>
  <p>But how can I handle the case, when no Moodle logout has been done?
  Looks like I need some way to tell keycloak to do backchannel logout's to moodle...</p>
  <p>We use the miniOrange SSO plugin in Moodle 3.11.3+</p>