XML::Feed::Util::format_w3cdtf function returns wrong value for a DateTime object with non-UTC time zone.
use DateTime;
use XML::Feed::Util qw(format_w3cdtf);
say format_w3cdtf(DateTime->now(time_zone => 'Asia/Tokyo'));
# Actual: 2021-05-20T18:02:33+09:00Z
# Expected: 2021-05-20T18:02:33+09:00
XML::Feed::Util::format_w3cdtf
function returns wrong value for aDateTime
object with non-UTC time zone.