message: Simplify era ID in logs.
diff: @@ -314,7 +314,7 @@ where
  %start_time,
  %timestamp,
  %start_height,
  - %era_id,
  + era = era_id.0,
  "starting era",
  );
  // For Highway, we need u64 weights. Scale down by sum / u64::MAX, rounded up.
  @@ -356,11 +356,11 @@ where
  );
  let results = if should_activate {
  - info!(%era_id, "start voting in era");
  + info!(era = era_id.0, "start voting");
  let secret = HighwaySecret::new(Rc::clone(&self.secret_signing_key), our_id);
  highway.activate_validator(our_id, secret, timestamp.max(start_time))
  } else {
  - info!(%era_id, "not voting in era");
  + info!(era = era_id.0, "not voting");
  if self.node_start_time >= start_time {
  info!(
  "node was started at time {}, which is not earlier than the era start {}",
  @@ -431,16 +431,16 @@ where
  match self.era_supervisor.active_eras.get_mut(&era_id) {
  None => {
  if era_id > self.era_supervisor.current_era {
  - info!(%era_id, "received message for future era");
  + info!(era = era_id.0, "received message for future era");
  } else {
  - info!(%era_id, "received message for obsolete era");
  + info!(era = era_id.0, "received message for obsolete era");
  }
  Effects::new()
  }
  Some(era) => match f(&mut *era.consensus, self.rng) {
  Ok(results) => self.handle_consensus_results(era_id, results),
  Err(error) => {
  - error!(%error, %era_id, "error while handling event in era");
  + error!(%error, era = era_id.0, "error while handling event");
  Effects::new()
  }
  },
  @@ -461,7 +461,7 @@ where
  match msg {
  ConsensusMessage::Protocol { era_id, payload } => {
  if era_id.0 + 2 * BONDED_ERAS < self.era_supervisor.current_era.0 {
  - trace!(%era_id, "not handling message; era too old");
  + trace!(era = era_id.0, "not handling message; era too old");
  return Effects::new();
  }
  // If the era is already unbonded, only accept new evidence, because still-bonded
  @@ -473,7 +473,7 @@ where
  }
  ConsensusMessage::EvidenceRequest { era_id, pub_key } => {
  if era_id.0 + BONDED_ERAS < self.era_supervisor.current_era.0 {
  - trace!(%era_id, "not handling message; era too old");
  + trace!(era = era_id.0, "not handling message; era too old");
  return Effects::new();
  }
  era_id
  @@ -591,7 +591,7 @@ where
  .consensus
  .deactivate_validator();
  let era_id = block_header.era_id().successor();
  - info!(%era_id, "era created");
  + info!(era = era_id.0, "era created");
  let seed = EraSupervisor::<I>::era_seed(booking_block_hash, key_block_seed);
  trace!(%seed, "the seed for {}: {}", era_id, seed);
  let results = self.era_supervisor.new_era(
  