code: function chatanglePayloadFromTransaction(transaction) {
      const transactionMessageObject = TryteEncoderDecoder.objectFromTritifiedJSON(transaction.signatureMessageFragment)
      if(!isValidChatangleTransactionMessageObject(transactionMessageObject)) { return }
  
      if(isEncrypted(transactionMessageObject)) {
          return chatanglePayloadFromEncryptedTransaction(transaction, transactionMessageObject)
      }
  
      return chatanglePayloadFromUnencryptedTransaction(transaction, transactionMessageObject)
  }
docs: Encrypted transaction message format:
  {
  "app": "Chatangle", // required
  "apiVersion": 1, // required
  "encryptedPayload": "base64EncodedPGPEncryptedJSONPayloadString" // base64(pgpEncrypt(JSON.stringify(payloadObject), password))
  }
   TODO: Handle multipart objects spread in a bundle across multiple transactions