Make JSON de/serializing of CipherText roundtrip

[LaurentRDC]

This is a small update to ensure that CipherText JSON de/serialization roundtrips.

This was tested using a script like so:

{-# LANGUAGE OverloadedStrings #-}

import qualified Data.ByteString.Base64 as B64
import Data.Text (Text)
import qualified Data.Text.Encoding as TE
import Network.VaultTool
import Network.VaultTool.Transit

main = do
    let vaultAddress = VaultAddress "..."
        vaultAuthToken = VaultAuthToken "..."
        vaultMountedPath = VaultMountedPath "transit"

        sensitiveInfo = "12345678" :: Text

        keyname = "..."

    manager <- defaultManager

    let conn = authenticatedVaultConnection manager vaultAddress vaultAuthToken

    CipherText b64 <-
        encryptBase64
            conn
            vaultMountedPath
            keyname
            (encodeBase64 $ TE.encodeUtf8 sensitiveInfo)

    xs <-
        either error TE.decodeUtf8Lenient
            . decodeBase64
            <$> decryptBase64
                conn
                vaultMountedPath
                keyname
                (CipherText b64)

    print xs