📍 feat: Preserve Deep Link Destinations Through the Auth Redirect Flow (#10275)

* added support for url query param persistance

* refactor: authentication redirect handling

- Introduced utility functions for managing login redirects, including `persistRedirectToSession`, `buildLoginRedirectUrl`, and `getPostLoginRedirect`.
- Updated `Login` and `AuthContextProvider` components to utilize these utilities for improved redirect logic.
- Refactored `useAuthRedirect` to streamline navigation to the login page while preserving intended destinations.
- Cleaned up the `StartupLayout` to remove unnecessary redirect handling, ensuring a more straightforward navigation flow.
- Added a new `redirect.ts` file to encapsulate redirect-related logic, enhancing code organization and maintainability.

* fix: enhance safe redirect validation logic

- Updated the `isSafeRedirect` function to improve validation of redirect URLs.
- Ensured that only safe relative paths are accepted, specifically excluding paths that lead to the login page.
- Refactored the logic to streamline the checks for valid redirect targets.

* test: add unit tests for redirect utility functions

- Introduced comprehensive tests for `isSafeRedirect`, `buildLoginRedirectUrl`, `getPostLoginRedirect`, and `persistRedirectToSession` functions.
- Validated various scenarios including safe and unsafe redirects, URL encoding, and session storage behavior.
- Enhanced test coverage to ensure robust handling of redirect logic and prevent potential security issues.

* chore: streamline authentication and redirect handling

- Removed unused `useLocation` import from `AuthContextProvider` and replaced its usage with `window.location` for better clarity.
- Updated `StartupLayout` to check for pending redirects before navigating to the new chat page, ensuring users are directed appropriately based on their session state.
- Enhanced unit tests for `useAuthRedirect` to verify correct handling of redirect parameters, including encoding of the current path and query parameters.

* test: add unit tests for StartupLayout redirect behavior

- Introduced a new test suite for the StartupLayout component to validate redirect logic based on authentication status and session storage.
- Implemented tests to ensure correct navigation to the new conversation page when authenticated without pending redirects, and to prevent navigation when a redirect URL parameter or session storage redirect is present.
- Enhanced coverage for scenarios where users are not authenticated, ensuring robust handling of redirect conditions.

---------

Co-authored-by: Vamsi Konakanchi <vamsi.k@trackmind.com>
Co-authored-by: Danny Avila <danny@librechat.ai>

client/src/components/Auth/Login.tsx

@@ -1,15 +1,19 @@
 import { useEffect, useState } from 'react';
 import { ErrorTypes, registerPage } from 'librechat-data-provider';
 import { OpenIDIcon, useToastContext } from '@librechat/client';
-import { useOutletContext, useSearchParams } from 'react-router-dom';
+import { useOutletContext, useSearchParams, useLocation } from 'react-router-dom';
 import type { TLoginLayoutContext } from '~/common';
+import { getLoginError, persistRedirectToSession } from '~/utils';
 import { ErrorMessage } from '~/components/Auth/ErrorMessage';
 import SocialButton from '~/components/Auth/SocialButton';
 import { useAuthContext } from '~/hooks/AuthContext';
-import { getLoginError } from '~/utils';
 import { useLocalize } from '~/hooks';
 import LoginForm from './LoginForm';
 
+interface LoginLocationState {
+  redirect_to?: string;
+}
+
 function Login() {
   const localize = useLocalize();
   const { showToast } = useToastContext();
@@ -17,13 +21,22 @@ function Login() {
   const { startupConfig } = useOutletContext<TLoginLayoutContext>();
 
   const [searchParams, setSearchParams] = useSearchParams();
-  // Determine if auto-redirect should be disabled based on the URL parameter
+  const location = useLocation();
   const disableAutoRedirect = searchParams.get('redirect') === 'false';
 
-  // Persist the disable flag locally so that once detected, auto-redirect stays disabled.
   const [isAutoRedirectDisabled, setIsAutoRedirectDisabled] = useState(disableAutoRedirect);
 
   useEffect(() => {
+    const redirectTo = searchParams.get('redirect_to');
+    if (redirectTo) {
+      persistRedirectToSession(decodeURIComponent(redirectTo));
+    } else {
+      const state = location.state as LoginLocationState | null;
+      if (state?.redirect_to) {
+        persistRedirectToSession(state.redirect_to);
+      }
+    }
+
     const oauthError = searchParams?.get('error');
     if (oauthError && oauthError === ErrorTypes.AUTH_FAILED) {
       showToast({
@@ -34,9 +47,8 @@ function Login() {
       newParams.delete('error');
       setSearchParams(newParams, { replace: true });
     }
-  }, [searchParams, setSearchParams, showToast, localize]);
+  }, [searchParams, setSearchParams, showToast, localize, location.state]);
 
-  // Once the disable flag is detected, update local state and remove the parameter from the URL.
   useEffect(() => {
     if (disableAutoRedirect) {
       setIsAutoRedirectDisabled(true);
@@ -46,7 +58,6 @@ function Login() {
     }
   }, [disableAutoRedirect, searchParams, setSearchParams]);
 
-  // Determine whether we should auto-redirect to OpenID.
   const shouldAutoRedirect =
     startupConfig?.openidLoginEnabled &&
     startupConfig?.openidAutoRedirect &&
@@ -60,7 +71,6 @@ function Login() {
     }
   }, [shouldAutoRedirect, startupConfig]);
 
-  // Render fallback UI if auto-redirect is active.
   if (shouldAutoRedirect) {
     return (
       <div className="flex min-h-screen flex-col items-center justify-center p-4">