ISO8601 Components Formatting and Parsing: https://github.com/swiftlang/swift-foundation/blob/main/Proposals/0021-ISO8601ComponentsStyle.md

I'm going to label this one #finally. Having to use a custom parser just because I wanted date components instead of a date was such a pain (for instance for a date only string).

As an added bonus it proposes making the parser more lenient by optionally allowing fractional seconds and hours-only time zone offsets.