Add ability to logout from OIDC (#6539)

* Add OIDC_LOGOUT_URI functionality

* Add logout redirect to work on logout route

* Fix lint

* Fix lint

* Fix lint

* Fix lint

* Return null if logout endpoint used

* Update import

app/scenes/Logout.tsx

@@ -1,10 +1,15 @@
 import * as React from "react";
 import { Redirect } from "react-router-dom";
+import env from "~/env";
 import useStores from "~/hooks/useStores";
 
 const Logout = () => {
   const { auth } = useStores();
   void auth.logout();
+  if (env.OIDC_LOGOUT_URI) {
+    window.location.replace(env.OIDC_LOGOUT_URI);
+    return null;
+  }
   return <Redirect to="/" />;
 };