Replace ToJSON/FromJSON Tx with cbor encoding

hydra-node/src/Hydra/Ledger/Cardano.hs

@@ -28,6 +28,7 @@ import Cardano.Ledger.Shelley.UTxO qualified as Ledger
 import Codec.CBOR.Decoding qualified as CBOR
 import Codec.CBOR.Encoding qualified as CBOR
 import Control.Monad (foldM)
+import Data.Aeson qualified as Aeson
 import Data.ByteString qualified as BS
 import Data.Default (def)
 import Data.Map.Strict qualified as Map
@@ -125,10 +126,13 @@ instance FromCBOR Tx where
         (pure . fromLedgerTx)
 
 instance ToJSON Tx where
-  toJSON = toJSON . toLedgerTx
+  toJSON tx = Aeson.String $ decodeUtf8 @Text $ serialiseToCBOR tx
 
 instance FromJSON Tx where
-  parseJSON = fmap fromLedgerTx . parseJSON
+  parseJSON v = do
+    bytes <- encodeUtf8 @Text <$> parseJSON v
+    let cbor = deserialiseFromCBOR (proxyToAsType @Tx Proxy) bytes
+    either (fail . show) pure cbor
 
 instance Arbitrary Tx where
   -- TODO: shrinker!