[Proposal] SLG-0004: Metadata values privacy attribute

[FranzBusch]

@johannesweiss

You mean essentially we'd specify a fixed OptionSet of privacyPrivate, privacyPublic, privacyRestricted, systemMetric, typeInt, typeFloat, typeString, typeBool, typeURL, ... in swift-log itself instead of making this extensible by others? It would of course make the "registration aspect" easy because there's a fixed list. I don't love it, I don't hate it.

Correct. I think we have somewhat reached consensus here that there is a value in additional attributes for metadata values with privacy levels being one of them. I think fully generalized metadata attributes are interesting but bring a lot of complexity. I think we should start with a small and strongly opinionated set from swift-log. In the future, we can explore extending this to customizable attributes, but I remain skeptical that this won't lead to a tighter coupling of libraries and log handlers.