Function caller_middleware 

pub(crate) async fn caller_middleware(
    __arg0: State<AppState>,
    req: Request<Body>,
    next: Next,
) -> Response

Inserts Caller. Layered inside auth_middleware / lan_or_full_auth_middleware; both mark which key authenticated the request (ReactiveAuthVia), and a Caller is derived only when that mark says the full key — a request that reached here unmarked is Unattributed, never assumed full-key (review on #3571). The WebSocket upgrade is always Unattributed (§6.5.3): WebSocket RPC is the UI’s channel, and a token must never ride on it.