message: add handy accessors to the Leadership object
  this allows to get the necessary information from the leadership
  to check consistency of the leadership
diff: @@ -145,6 +145,18 @@ impl Leadership {
  }
  }
  + /// get the epoch associated to the `Leadership`
  + #[inline]
  + pub fn epoch(&self) -> Epoch {
  + self.epoch
  + }
  +
  + /// get the TimeEra associated to the `Leadership`
  + #[inline]
  + pub fn era(&self) -> &TimeEra {
  + &self.era
  + }
  +
  /// Verify whether this header has been produced by a leader that fits with the leadership
  ///
  pub fn verify(&self, block_header: &Header) -> Verification {
  