re-implemented login via OIDC

frontend/src/App.svelte

@@ -3,6 +3,7 @@
     import { loadTranslation } from './translations.svelte.js';
     import { user } from './user.svelte.js';
     import { Router, Route } from 'svelte-tiny-router';
+    import Callback from "./routes/user/OidcCallback.svelte";
     import EditService from "./routes/user/EditService.svelte";
     import Footer   from "./Components/Footer.svelte";
     import Login    from "./Components/Login.svelte";
@@ -26,9 +27,9 @@
 </script>
 
 {#if translations_ready }
+    <Router>
     {#if user.name }
         <!-- https://github.com/notnotsamuel/svelte-tiny-router -->
-        <Router>
             <Menu />
             <Route path="/user" component={User} />
             <Route path="/user/:user_id/edit" component={UserEdit} />
@@ -36,10 +37,11 @@
             <Route>
                 <p>Page not found</p>
             </Route>
-        </Router>
     {:else}
         <Login />
+        <Route path="/oidc_callback" component={Callback} />
     {/if}
+    </Router>
     <Footer />
 {:else}
     <p>Loading translations...</p>