DefaultSetting returns a Setting representing "use the default".

DisabledSetting returns a Setting representing "disable the timeout".

DurationSetting returns a timeout setting with the given duration.

Parse parses string representations of timeout settings that we pass in various places in a standard way: - an empty string means "use the default".

ParseMaxAge parses string representations of "max age" values used mostly in cache related settings.

Setting describes a timeout setting that can be exactly one of: disable the timeout entirely, use the default, or use a specific value.