Filter flash to only display info, success and error messages.
Filter flash to only display info, success and error messages.

Avoid displaying [flash commands](https://github.com/moneyadviceservice/public_website/blob/master/app/controllers/commands/command_helper.rb) set by the public website.

moneyadviceservice/frontend,moneyadviceservice/frontend,moneyadviceservice/frontend,moneyadviceservice/frontend