JSONC in external services config causes 500

Created by: chrismwendt

• Open http://localhost:3080/site-admin/external-services
• Create a new service
• Save the default text (make sure it includes a comment // ...):

{
    // Configure your external service here (Ctrl+Space to see hints)
}

• Open http://localhost:3080/github.com/gorilla/mux/-/blob/mux.go
• Notice a 500: