feat: ledger support for TX certificates (#620)

This adds support for decoding the various certificate types available
in Shelley through Babbage for things like state pool registration and
delegation

Fixes #331

ledger/allegra.go

@@ -166,6 +166,10 @@ func (t AllegraTransaction) CollateralReturn() TransactionOutput {
 	return t.Body.CollateralReturn()
 }
 
+func (t AllegraTransaction) Certificates() []Certificate {
+	return t.Body.Certificates()
+}
+
 func (t AllegraTransaction) Metadata() *cbor.Value {
 	return t.TxMetadata
 }

ledger/alonzo.go

@@ -276,6 +276,10 @@ func (t AlonzoTransaction) CollateralReturn() TransactionOutput {
 	return t.Body.CollateralReturn()
 }
 
+func (t AlonzoTransaction) Certificates() []Certificate {
+	return t.Body.Certificates()
+}
+
 func (t AlonzoTransaction) Metadata() *cbor.Value {
 	return t.TxMetadata
 }

ledger/babbage.go

@@ -448,6 +448,10 @@ func (t BabbageTransaction) CollateralReturn() TransactionOutput {
 	return t.Body.CollateralReturn()
 }
 
+func (t BabbageTransaction) Certificates() []Certificate {
+	return t.Body.Certificates()
+}
+
 func (t BabbageTransaction) Metadata() *cbor.Value {
 	return t.TxMetadata
 }

ledger/byron.go

@@ -185,6 +185,11 @@ func (t *ByronTransaction) CollateralReturn() TransactionOutput {
 	return nil
 }
 
+func (t *ByronTransaction) Certificates() []Certificate {
+	// No certificates in Byron
+	return nil
+}
+
 func (t *ByronTransaction) Metadata() *cbor.Value {
 	return t.Attributes
 }