docs(session): show a login that sets session.user

docs/SESSION.md

@@ -176,6 +176,13 @@ async def account(session: AuthenticatedSession):
 `UserSessionDep` does not check for a user despite its name; it is an alias of `SessionDep`
 until 0.4.0, which is planned to make it require one.
 
+`session.user` is set only by passing `user=` to `create_session()` or by assigning it and
+saving the session. Keys written to `request.session` (`request.session["user_id"] = ...`)
+are application data: the library does not treat them as a login, so `AuthenticatedSession`
+still answers `401` for such a session. See
+[Regenerate the Session ID After Login](#5-regenerate-the-session-id-after-login) for a login
+that sets the user.
+
 ### 3. Full Example (Redis Backend)
 
 ```python
@@ -670,6 +677,37 @@ A handler that already holds the request's session object can call
 `get_optional_session` and skip the call when it is `None`; `SessionDep` answers `401` to a
 visitor who has no session yet.
 
+The example above stores the user ID as application data, which `require_user_session` and
+`AuthenticatedSession` do not recognise. To pass them, attach a `SessionUser` after the
+rotation and save the session yourself: assigning `session.user` does not mark
+`request.session` as modified, so the middleware would not save it.
+
+```python
+from fastapi_cachex.session import SessionUser
+from fastapi_cachex.session.dependencies import OptionalSession
+
+
+@app.post("/login")
+async def login(request: Request, session: OptionalSession):
+    ...  # verify the credentials
+    user = SessionUser(user_id="123")
+    if session is not None:
+        await rotate_session_id(request)
+        session.user = user
+        await session_manager.update_session(session)
+    else:
+        # No session yet: create one with the user and deliver its token yourself,
+        # as in the login example in Basic Usage.
+        _, token = await session_manager.create_session(user=user)
+        ...
+    return {"ok": True}
+```
+
+The complete version, including the cookie for a new visitor, is
+[`examples/session_login.py`](https://github.com/allen0099/FastAPI-CacheX/blob/master/examples/session_login.py).
+A `login()` helper that does all of this is planned
+([#293](https://github.com/allen0099/FastAPI-CacheX/issues/293)).
+
 Outside a middleware, load the session with the same bindings the middleware would pass, and hand
 the returned token to the client yourself:
 

fastapi_cachex/session/dependencies.py

@@ -176,6 +176,11 @@ async def login(request: Request):
             return {"ok": True}
         ```
 
+        ``request.session["user_id"]`` is application data. For
+        ``require_user_session`` / ``AuthenticatedSession`` to accept the
+        session, set ``session.user`` after the rotation and save it with
+        ``SessionManager.update_session()``; see the session guide.
+
     Args:
         request: FastAPI request object
 

i18n/zh-TW/docs/SESSION.md

@@ -154,6 +154,8 @@ async def account(session: AuthenticatedSession):
 
 `UserSessionDep` 雖然名稱如此，卻不會檢查使用者；在 0.4.0 之前它是 `SessionDep` 的別名，0.4.0 預計改為要求使用者。
 
+只有在 `create_session()` 傳入 `user=`，或指定 `session.user` 後儲存 Session，才會設定 `session.user`。寫入 `request.session` 的鍵（`request.session["user_id"] = ...`）是應用程式資料：函式庫不會把它視為登入，因此這種 Session 仍會讓 `AuthenticatedSession` 回應 `401`。會設定使用者的登入方式，請見[登入後重新產生 Session ID](#5-regenerate-the-session-id-after-login)。
+
 ### 3. 完整範例（Redis 後端） {#3-full-example-redis-backend}
 
 ```python
@@ -544,6 +546,31 @@ async def login(request: Request):
 
 已經取得請求 Session 物件的 handler，也可以直接呼叫 `await manager.regenerate_session_id(session)`，效果相同。請從 `get_optional_session` 取得 Session，並在它為 `None` 時略過呼叫；`SessionDep` 會對還沒有 Session 的訪客回應 `401`。
 
+上面的範例把使用者 ID 存成應用程式資料，`require_user_session` 與 `AuthenticatedSession` 不會認得它。要通過它們的檢查，請在換 ID 之後附加 `SessionUser`，並自行儲存 Session：指定 `session.user` 不會把 `request.session` 標記為已修改，因此中介軟體不會儲存它。
+
+```python
+from fastapi_cachex.session import SessionUser
+from fastapi_cachex.session.dependencies import OptionalSession
+
+
+@app.post("/login")
+async def login(request: Request, session: OptionalSession):
+    ...  # 驗證帳號密碼
+    user = SessionUser(user_id="123")
+    if session is not None:
+        await rotate_session_id(request)
+        session.user = user
+        await session_manager.update_session(session)
+    else:
+        # 還沒有 Session：建立帶有使用者的 Session，並自行交付其權杖，
+        # 做法同基本用法中的登入範例。
+        _, token = await session_manager.create_session(user=user)
+        ...
+    return {"ok": True}
+```
+
+完整版本（包含為新訪客設定 Cookie）請見 [`examples/session_login.py`](https://github.com/allen0099/FastAPI-CacheX/blob/master/examples/session_login.py)。處理上述所有步驟的 `login()` 輔助函式已在規劃中（[#293](https://github.com/allen0099/FastAPI-CacheX/issues/293)）。
+
 在中介軟體之外，請以中介軟體會傳入的相同綁定值載入 Session，並自行將回傳的權杖交給用戶端：
 
 ```python