Feature: Reverse proxy authentication (#455)

- Changes the auth settings to support more than two auth types
- Added a proxy auth type with settings for user and optionally group
headers
- Added a global middleware `proxy_auth_middleware` to handle proxy auth
(it does nothing if any other auth mode is set)
- Added support for proxy auth to `get_auth_mode`, `login_required`,
`api_login/out`, and `api_auth_check`
- Added a backend check to make protect the API for settings when admin
is required

---------

Co-authored-by: Joshua Tag Howard <git@jthoward.dev>
Co-authored-by: Alex <alex.bilbie1@gmail.com>

src/frontend/src/hooks/useAuth.ts

@@ -83,7 +83,11 @@ export function useAuth(options: UseAuthOptions = {}): UseAuthReturn {
 
   const handleLogout = useCallback(async () => {
     try {
-      await logout();
+      const { logout_url } = await logout();
+      if (logout_url?.startsWith('https://') || logout_url?.startsWith('http://')) {
+        window.location.href = logout_url;
+        return;
+      }
       setIsAuthenticated(false);
       onLogoutSuccess?.();
       navigate('/login', { replace: true });

src/frontend/src/types/index.ts

@@ -181,6 +181,7 @@ export interface AuthResponse {
   auth_required?: boolean;
   is_admin?: boolean;
   error?: string;
+  logout_url?: string;
 }
 
 // Type guard to check if a book is from a metadata provider