[Misc] centralize all usage of environment variables (#4548)

vllm/entrypoints/openai/api_server.py

@@ -1,7 +1,6 @@
 import asyncio
 import importlib
 import inspect
-import os
 import re
 from contextlib import asynccontextmanager
 from http import HTTPStatus
@@ -16,6 +15,7 @@ from prometheus_client import make_asgi_app
 from starlette.routing import Mount
 
 import vllm
+import vllm.envs as envs
 from vllm.engine.arg_utils import AsyncEngineArgs
 from vllm.engine.async_llm_engine import AsyncLLMEngine
 from vllm.entrypoints.openai.cli_args import make_arg_parser
@@ -129,7 +129,7 @@ if __name__ == "__main__":
         allow_headers=args.allowed_headers,
     )
 
-    if token := os.environ.get("VLLM_API_KEY") or args.api_key:
+    if token := envs.VLLM_API_KEY or args.api_key:
 
         @app.middleware("http")
         async def authentication(request: Request, call_next):