UPDATE OAuth2 user service to handle user creation and redirect after login

frontend/src/components/Topbar.tsx

@@ -9,13 +9,18 @@ type props = {
 }
 
 const Topbar = ({sidebarToggled, setSidebarToggled, className}: props) => {
+    const apiUrl = import.meta.env.VITE_API_URL;
+    const redirectUri = encodeURIComponent(window.location.href);
+    const loginUrl = `${apiUrl}/oauth2/authorization/google?redirect_uri=${redirectUri}`;
+
     return (
         <div className={clsx(className, "flex justify-between")}>
             <MenuButton onClick={() => setSidebarToggled(!sidebarToggled)}>
                 {sidebarToggled ? <Menu size={24}/> :  <X size={24}/>}
             </MenuButton>
 
-            <MenuButton className={"w-20 text-gray-600"}>
+            <MenuButton className={"w-20 text-gray-600"}
+            onClick={() => globalThis.location.href = loginUrl}>
                 Login
             </MenuButton>
         </div>