Macro event 

macro_rules! event {
    ($event_name:expr $(, $key:expr => $value:expr)* $(,)?) => { ... };
}

Adds an event to the current span with optional attributes.

Examples

// Simple event
otel::event!("query.start");

// Event with attributes
otel::event!("query.result",
  "record_count" => 42,
  "partition_key" => "users"
);