Double quotes in messsage return are not escaped

[ereslibre]

If the user adds a double quote to the message either in RejectRequest or RejectSettings, the go SDK does not properly escape them and an invalid JSON is produced that will later be troublesome, either for the policy-server or for kwctl through the policy-evaluator.

We need to escape the JSON produced by the policy author, but given the limitations of TinyGo this does not seem to be a trivial operation.