DateTime parsing is incorrect

[aliotta]

Scim defines its datetime field (https://datatracker.ietf.org/doc/html/rfc7643#section-2.3.5) as following the w3 xsd schema (https://www.w3.org/TR/xmlschema11-2/#dateTime). Currently the dateTime validation fails for dateTime with timezones +00:00. Modifying the fromIso method to the bellow seems to do the trick.

func (p *dateTimeProperty) fromISO8601(str string) (time.Time, error) {
	const DateTimeFormat     = "2006-01-02T15:04:05.999999999-07:00"
	const DateTimeNoTimezone = "2006-01-02T15:04:05.999999999"
	const DateTimeUTC        = "2006-01-02T15:04:05.999999999Z"
	var (
		val time.Time
		err error
		z   = str[len(str)-6]
		utc = str[len(str)-1]
	)

	if z == '+' || z == '-' {
		val, err = time.Parse(DateTimeFormat, str)
	} else if utc == 'Z' {
		val, err = time.Parse(DateTimeUTC, str)
	} else {
		val, err = time.Parse(DateTimeNoTimezone, str)
	}

	if err != nil {
		return time.Time{}, fmt.Errorf("%w, value for '%s' does not conform to ISO8601", spec.ErrInvalidValue, p.attr.Path())
	}

	return val, nil

}

[imulab]

I have always been aware of this problem, but unable to solve it. Thanks a lot for contributing the above snippet. I will take a look and make some test cases.