fix: fix Json serialisation error when packing forward message for me…

…diator

Signed-off-by: Benjamin Voiturier <benjamin.voiturier@iohk.io>

mercury/models/src/main/scala/org/hyperledger/identus/mercury/model/EncryptedMessage.scala

@@ -1,15 +1,16 @@
 package org.hyperledger.identus.mercury.model
 
 import zio.json.ast.Json
-import zio.json.EncoderOps
+import zio.json.DecoderOps
 
 import java.util.Base64
 
 trait EncryptedMessage { // (private val msg: PackEncryptedResult) {
   def string: String // = msg.getPackedMessage
   def base64: String = Base64.getUrlEncoder.encodeToString(string.getBytes)
   def asJson: Json.Obj = {
-    string.toJsonAST
+    string
+      .fromJson[Json]
       .flatMap(o =>
         o.asObject match
           case None        => Left(RuntimeException(s"Expecting Json Object got '$o'"))