Centralize logout method; delete OIDC sessions on logout

app/controllers/saml/SAML.controller.js

@@ -19,7 +19,6 @@ class SAMLController extends Controller {
         })(req, res, next)
     }
 
-    // TODO some sort of first-logon flow
     async get_sso(req, res, next) {
         const index = await req.saml.participants.issue({ service_provider: req.saml_request.service_provider })
 
@@ -71,7 +70,7 @@ class SAMLController extends Controller {
                 this.output.info(`${req.T('saml.clear_idp_session')} ${req.user.uid}`)
                 req.saml.participants.clear().then(async () => {
                     if ( this.saml.config().slo.end_coreid_session ) {
-                        await req.user.get_provider().logout(req)
+                        await req.user.logout(req)
 
                         // show logout page
                         return this.Vue.auth_message(res, {