Function apply_request_deadline 

pub fn apply_request_deadline<T>(
    request: &mut Request<T>,
    headers: &HeaderMap,
) -> Option<Duration>

Apply a client-supplied deadline to the upstream gRPC call.

Reads the gRPC-standard grpc-timeout header (<int><unit>, unit one of H/M/S/m/u/n) and sets it as the request timeout, which travels to the upstream as its grpc-timeout. Absent or malformed values set nothing, leaving the proxy’s own UPSTREAM_DEADLINE. Returns the deadline that was applied, if any.