message: time: add missing derivation and make slots_per_epoch public
diff: @@ -19,11 +19,11 @@ pub struct EpochPosition {
  /// Describe a new era, which start at epoch_start and is associated
  /// to a specific slot. Each epoch have a constant number of slots on a given time era.
  -#[derive(Debug, Clone)]
  +#[derive(Debug, Clone, PartialEq, Eq)]
  pub struct TimeEra {
  epoch_start: Epoch,
  slot_start: Slot,
  - slots_per_epoch: u32,
  + pub slots_per_epoch: u32,
  }
  impl TimeEra {
  