support RFC 9557 (Internet Extended Date/Time Format a.k.a. IXDTF)

[derhuerst]

Is your feature request related to a problem? Please describe.

It seems to me that, until recently, there was no standardised and widely used serialisation format to express a date & time within a certain (IANA) time zone. The only thing I know of is the Java ISO_ZONED_DATE_TIME format. Recently, RFC 9557 has been published, standardising a very similar format that allows exactly this.

From my personal experience, this use case is very common. I usually solve it by accepting an ISO 8601/RFC 3339 date/time string along with a IANA tz database identifier, e.g. as two fields in a JSON object. The newly standardised format looks like it might become the de-facto standard for this use case.

Describe the solution you'd like

I'd love Luxon to support another parser/constructor (e.g. DateTime.fromIXDTF(ixdtf, options)) and another serialiser (e.g. dt.toIXDTF()).

Describe alternatives you've considered

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Additional context

• RFC 9557
• RFC 3339
• I'm not an expert on date/time logic & serialisation formats!