* 그래서 사용자는 나중에 어느 시점엔 다시 로그인해야 합니다.
        * 그리고 token이 도난당하더라도 위험이 더 낮습니다. 대부분의 경우 영구적으로 항상 동작하는 키와는 다릅니다.
* frontend는 그 token을 임시로 어딘가에 저장합니다.
* 사용자가 frontend에서 클릭해서 frontend 웹 앱의 다른 섹션으로 이동합니다.
* frontend는 API에서 더 많은 데이터를 가져와야 합니다.
    * 하지만 그 특정 endpoint에는 인증이 필요합니다.
    * 그래서 우리 API에 인증하기 위해 `Authorization` 헤더를, 값은 `Bearer `에 token을 더한 형태로 보냅니다.

  - 💾 [PostgreSQL](https://www.postgresql.org) as the SQL database.
- 🚀 [React](https://react.dev) for the frontend.
  - 💃 Using TypeScript, hooks, Vite, and other parts of a modern frontend stack.
  - 🎨 [Tailwind CSS](https://tailwindcss.com) and [shadcn/ui](https://ui.shadcn.com) for the frontend components.
  - 🤖 An automatically generated frontend client.
  - 🧪 [Playwright](https://playwright.dev) for End-to-End testing.
  - 🦇 Dark mode support.

        * And if the token is stolen, the risk is less. It is not like a permanent key that will work forever (in most of the cases).
* The frontend stores that token temporarily somewhere.
* The user clicks in the frontend to go to another section of the frontend web app.
* The frontend needs to fetch some more data from the API.
    * But it needs authentication for that specific endpoint.

[CORS or "Cross-Origin Resource Sharing"](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) refers to the situations when a frontend running in a browser has JavaScript code that communicates with a backend, and the backend is in a different "origin" than the frontend.

## Origin { #origin }

Imagine you build a way to run a local AI agent.

It provides an API at

```
http://localhost:8000/v1/agents/multivac
```

There's also a frontend at

```
http://localhost:8000
```

/// tip

Note that both have the same host.

///

Then using the frontend you can make the AI agent do things on your behalf.

```console
$ pip install websockets

---> 100%
```

</div>

## WebSockets client { #websockets-client }

### In production { #in-production }

In your production system, you probably have a frontend created with a modern framework like React, Vue.js or Angular.

And to communicate using WebSockets with your backend you would probably use your frontend's utilities.

But then, when you open the integrated docs UI (the frontend), it would expect to get the OpenAPI schema at `/openapi.json`, instead of `/api/v1/openapi.json`.

So, the frontend (that runs in the browser) would try to reach `/openapi.json` and wouldn't be able to get the OpenAPI schema.

Because we have a proxy with a path prefix of `/api/v1` for our app, the frontend needs to fetch the OpenAPI schema at `/api/v1/openapi.json`.

## i18n / Localization
- This project supports up to 21 languages. When modifying user-facing strings, error codes, or labels, always propagate changes to ALL language files (fess_label_*.properties and frontend i18n files).

## Important Patterns for AI Assistants

### Do's
1. Use `@Resource` for field injection (not constructor injection)
2. Access helpers via `ComponentUtil.getXyzHelper()`

      Map<? extends Class<? extends S>, ? extends S> map) {
    if (map instanceof ImmutableClassToInstanceMap) {
      @SuppressWarnings("rawtypes") // JDT-based J2KT Java frontend does not permit the direct cast
      Map rawMap = map;
      @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
      ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap<B>) rawMap;

      Map<? extends Class<? extends S>, ? extends S> map) {
    if (map instanceof ImmutableClassToInstanceMap) {
      @SuppressWarnings("rawtypes") // JDT-based J2KT Java frontend does not permit the direct cast
      Map rawMap = map;
      @SuppressWarnings("unchecked") // covariant casts safe (unmodifiable)
      ImmutableClassToInstanceMap<B> cast = (ImmutableClassToInstanceMap<B>) rawMap;