retrieve the TimeEra of a given Ledger state

this will allow retrieving the associated settings of the given TimeEra
(num epoch per blocks) as well as retrieving the associated chain-time::Slot
of the given State

chain-impl-mockchain/src/ledger.rs

@@ -487,6 +487,13 @@ impl Ledger {
         self.date
     }
 
+    /// get the TimeEra associated to the given Ledger state
+    /// This allows retrieving the current ledger `Slot` but also
+    /// get the current time settings
+    pub fn era(&self) -> &TimeEra {
+        &self.settings.era
+    }
+
     fn validate_utxo_total_value(&self) -> Result<(), Error> {
         let old_utxo_values = self.oldutxos.iter().map(|entry| entry.output.value);
         let new_utxo_values = self.utxos.iter().map(|entry| entry.output.value);