Unneeded character escaping for Slack/SlackRecord

[alies-dev]

The only one goal of using json_encode to prepare $record to send to slack is to stringify some types for better perception. json_encode uses flash escaping by default that provides bad user experience, especially for URL:

[Seldaek]

Thanks for the fix, but it kinda conflicted with other changes I did to fix broader json encoding issues so I had to reimplement it. In any case it should now be fixed in the latest release