Fix webfinger support for custom domains

app/main.py

@@ -1256,7 +1256,7 @@ async def post_remote_interaction(
 @app.get("/.well-known/webfinger")
 async def wellknown_webfinger(resource: str) -> JSONResponse:
     """Exposes/servers WebFinger data."""
-    if resource not in [f"acct:{USERNAME}@{DOMAIN}", ID]:
+    if resource not in [f"acct:{USERNAME}@{WEBFINGER_DOMAIN}", ID]:
         logger.info(f"Got invalid req for {resource}")
         raise HTTPException(status_code=404)