refactor(api): migrate JSON instances to Exp.IsEra constraints

Refactors ToJSON/FromJSON instances for key types to use the new
Exp.IsEra constraint system instead of the legacy IsShelleyBasedEra
and IsCardanoEra constraints. This modernizes the codebase to use
the experimental era infrastructure while maintaining backwards
compatibility.

- Migrate AddressInEra JSON instances to use Exp.IsEra
- Update ReferenceScript serialization to use new constraints
- Refactor TxOut (CtxTx and CtxUTxO) JSON parsing to use Exp.convert
- Simplify TxOutValue JSON handling with unified era conversion
- Consolidate duplicate parsing logic for Babbage/Conway/Dijkstra eras
- Remove era-specific case matching in favor of generic implementations

The refactoring eliminates significant code duplication by using the
convert function to obtain appropriate era witnesses, making the code
more maintainable while preserving the exact JSON format.

Author: newhoggy

cardano-api/src/Cardano/Api/Address.hs

@@ -90,6 +90,7 @@ where
 
 import Cardano.Api.Byron.Internal.Key
 import Cardano.Api.Era
+import Cardano.Api.Experimental.Era qualified as Exp
 import Cardano.Api.HasTypeProxy
 import Cardano.Api.Key.Internal
 import Cardano.Api.Monad.Error
@@ -370,12 +371,13 @@ data AddressInEra era where
 instance NFData (AddressInEra era) where
   rnf (AddressInEra t a) = deepseq (deepseq t a) ()
 
-instance IsCardanoEra era => ToJSON (AddressInEra era) where
-  toJSON = Aeson.String . serialiseAddress
+instance Exp.IsEra era => ToJSON (AddressInEra era) where
+  toJSON = Exp.obtainCommonConstraints (Exp.useEra @era) $
+    Aeson.String . serialiseAddress
 
-instance IsShelleyBasedEra era => FromJSON (AddressInEra era) where
+instance Exp.IsEra era => FromJSON (AddressInEra era) where
   parseJSON =
-    let sbe = shelleyBasedEra @era
+    let sbe = convert (Exp.useEra @era)
      in withText "AddressInEra" $ \txt -> do
           addressAny <- P.runParserFail parseAddressAny txt
           pure $ anyAddressInShelleyBasedEra sbe addressAny

cardano-api/src/Cardano/Api/Plutus/Internal/Script.hs

@@ -125,6 +125,7 @@ import Cardano.Api.Era.Internal.Core
 import Cardano.Api.Era.Internal.Eon.BabbageEraOnwards
 import Cardano.Api.Era.Internal.Eon.ShelleyBasedEra
 import Cardano.Api.Error
+import Cardano.Api.Experimental.Era qualified as Exp
 import Cardano.Api.HasTypeProxy
 import Cardano.Api.Hash
 import Cardano.Api.Key.Internal
@@ -1647,16 +1648,14 @@ deriving instance Eq (ReferenceScript era)
 
 deriving instance Show (ReferenceScript era)
 
-instance IsCardanoEra era => ToJSON (ReferenceScript era) where
+instance Exp.IsEra era => ToJSON (ReferenceScript era) where
   toJSON (ReferenceScript _ s) = object ["referenceScript" .= s]
   toJSON ReferenceScriptNone = Aeson.Null
 
-instance IsCardanoEra era => FromJSON (ReferenceScript era) where
+instance Exp.IsEra era => FromJSON (ReferenceScript era) where
   parseJSON = Aeson.withObject "ReferenceScript" $ \o ->
-    caseByronToAlonzoOrBabbageEraOnwards
-      (const (pure ReferenceScriptNone))
-      (\w -> ReferenceScript w <$> o .: "referenceScript")
-      (cardanoEra :: CardanoEra era)
+    let w = Exp.convert (Exp.useEra @era)
+     in ReferenceScript w <$> o .: "referenceScript"
 
 refScriptToShelleyScript
   :: ShelleyBasedEra era