ISO8601DateFormatter fails to parse a valid ISO-8601 date

Using Swift
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12

AFAICS, the solution is simple. We just need to change one line of JSONEncoder.swift.
Where the _iso8601Formatter is being created:

private var _iso8601Formatter: ISO8601DateFormatter = {
    let formatter = ISO8601DateFormatter()
    formatter.formatOptions = .withInternetDateTime
    return formatter
}()

needs to be changed to:

private var _iso8601Formatter: ISO8601DateFormatter = {
    let formatter = ISO8601DateFormatter()
    formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
    return formatter
}()

But by this change 'fractions of second' becomes mandatory. A workaround could be adding a associated value to .iso8601 case where we can specify if withFractionalSeconds must be included in formatOptions or not. A less efficient solution is trying to decode data without .withFractionalSeconds first and if the result is nil, trying again but this time with .withFractionalSeconds. Also, we can add a new case to DateEncodingStrategy, .iso8601FractionalSeconds.

Any way, I guess the right direction is to pitch a proposal in this forum.