Macro otel_span 

macro_rules! otel_span {
    ($Name:expr, $Start:expr, $Attrs:expr) => { ... };
    ($Name:expr, $Start:expr) => { ... };
}

Convenience macro: emit an OTLP span for a Grove handler. Usage: otel_span!("grove:activate", StartNano, &[("extension", &Id)]);