message: Add doc comment to the `ScopeTimer` struct
diff: @@ -36,6 +36,11 @@ use crate::{
  utils::work_queue::WorkQueue,
  };
  +/// Helper struct that is used to measure a time spent in the scope.
  +/// At the construction time, a reference to the gauge is provided. When the binding to `ScopeTimer`
  +/// is dropped, the specified gauge is updated with the duration since the scope was entered.
  +// In the future, this could be replaced with a mechanism that uses `tracing::instrument` attribute
  +// macro.
  struct ScopeTimer<'a> {
  start: Instant,
  gauge: &'a IntGauge,
  