Set autogenerated guest username

src/ErrorModal.jsx

@@ -0,0 +1,30 @@
+import React, { useEffect } from "react";
+import { Center, Content, Modal } from "./Layout";
+import { Link } from "react-router-dom";
+import { ErrorMessage } from "./Input";
+import styles from "./ErrorModal.module.css";
+
+export function ErrorModal({ error }) {
+  useEffect(() => {
+    console.error(error);
+  }, [error]);
+
+  return (
+    <Content>
+      <Center>
+        <Modal>
+          <h2>Error</h2>
+          <div className={styles.errorModalContent}>
+            <ErrorMessage>{error.message}</ErrorMessage>
+            <p>
+              <Link to="/login">Login</Link>
+            </p>
+            <p>
+              <Link to="/register">Register</Link>
+            </p>
+          </div>
+        </Modal>
+      </Center>
+    </Content>
+  );
+}