Edit history: ISO8601 timestamp input fields do not accept "+00:00" as zone designator, only "Z"

Observed behaviour

The parser for ISO8601 is overly restrictive - it only allows "Z" as the zone designator but not "+00:00". While I can understand not wanting to support iso8601 timestamp in non-UTC timezones due to added complexity, it would be good to at least support both ways of specifying that the timestamp is in UTC that ISO8601 allows (since it's just a matter of expanding the regex for the zone designator part to be (Z|\+00:00) rather than just Z). Especially since some programming languages may choose to output ISO8601 timestamps with +00:00 rather than Z (as is the case in Python's datetime.datetime.isoformat(), for example). Also, limitations of what can be parsed should be documented.

Reproduction steps

Make an API request to any endpoint requring ISO8601 timestamp with a "+00:00" instead of "Z" use as the zone designator, e.g. "2026-09-07T18:33:12.120000+00:00"
See "The provided value is in an invalid format" error returned by the API.

As a concrete example:

PATCH /guilds/{guild.id}/members/{member.id}

{"communication_disabled_until":"2026-09-07T18:33:12.120000+00:00"}

Results in:

{
    "code": "INVALID_FORM_BODY",
    "message": "Invalid form body.",
    "errors": [
        {
            "path": "communication_disabled_until",
            "message": "The provided value is in an invalid format.",
            "code": "INVALID_FORMAT"
        }
    ]
}

Build information

This is an API issue, so not relevant.

Platform

API

Evidence

Everything relevant has already been presented above.