Allowlist for local client configuration via Fast Flags

[Dogekidd2012]

@BritishTrainspotting

I also agree, furthermore I thik the fastflag whitelist should instead be a blacklist for known bad flags. It is the job of your developers to ensure that fastflags that could be abused are either not pushed to global release or simply have bounds so that abnormal vlaues cannot be exploited.

As said before, this is not going to happen. We do not see it as the job of engineers to ensure that flags cannot be used inappropriately when flags are intended as a release mechanism:

Fast flags are being used as cheats

This behavior will not be preserved in the client, though you will still be able to change flags in Studio using whatever method you would be using today. This simply isn’t sustainable and requires that we play cat and mouse and constantly make sure that specific FFlags can’t be abused. Also, even if this was added, it certainly wouldn’t include reverting to old CoreGui, as the end state of most flags is for the code it’s replacing to be completely removed for maintainability reasons–we would …