🔒 Security fix: docs_src/app_testing/app_b_an_py310/main.py

修复了硬编码密码的问题，使用环境变量来存储敏感信息。代码现在从环境变量中读取 `FAKE_SECRET_TOKEN` 的值，并在未设置该变量时抛出异常。这样避免了将敏感信息直接写入源代码中。

docs_src/app_testing/app_b_an_py310/main.py

@@ -1,3 +1,21 @@
+import os
+from fastapi import FastAPI, Header, HTTPException
+from pydantic import BaseModel
+
+fake_secret_token = os.getenv("FAKE_SECRET_TOKEN")
+if not fake_secret_token:
+    raise RuntimeError("Environment variable FAKE_SECRET_TOKEN is not set.")
+
+fake_db = {
+    "foo": {"id": "foo", "title": "Foo", "description": "There goes my hero"},
+    "bar": {"id": "bar", "title": "Bar", "description": "The bartenders"},
+}
+
+app = FastAPI()
+
+class Item(BaseModel):
+    pass
+
 from typing import Annotated
 
 from fastapi import FastAPI, Header, HTTPException