message: add leadereship date_at_slot
diff: @@ -153,6 +153,19 @@ impl Leadership {
  self.epoch
  }
  + /// Create a Block date given a leadership and a relative epoch slot
  + ///
  + /// # Panics
  + ///
  + /// If the slot index is not valid given the leadership, out of bound date
  + pub fn date_at_slot(&self, slot_id: u32) -> BlockDate {
  + assert!(slot_id < self.era.slots_per_epoch());
  + BlockDate {
  + epoch: self.epoch(),
  + slot_id: slot_id,
  + }
  + }
  +
  /// get the TimeEra associated to the `Leadership`
  #[inline]
  pub fn era(&self) -> &TimeEra {
  