Add logout button in nav

ui/src/App.svelte

@@ -14,7 +14,7 @@
 </script>
 
 <Router url="{url}">
-  <Nav />
+  <Nav user="{user}" />
   <main role="main" class="container">
     <div>
       <Route path="client/:clientId" component="{EditClient}" />

ui/src/Nav.svelte

@@ -3,6 +3,8 @@
   import About from "./About.svelte";
   import Clients from "./Clients.svelte";
   import NavLink from "./NavLink.svelte";
+
+  export let user;
 </script>
 
 <header>
@@ -17,5 +19,12 @@
         <li class="nav-item"><NavLink to="about">About</NavLink></li>
       </ul>
     </div>
+
+    <div class="text-light">
+     <small>Logged in as {user}</small>
+     {#if user != "anonymous"}
+       <a class="btn btn-outline-light" href="/oauth2/sign_out">Log out</a>
+     {/if}
+    </div>
   </nav>
 </header>