CopyObject responses carried LastModified values such as
"2026-09-29T20:30:04.56Z": trailing zeros of the fractional seconds were
trimmed, and a whole-second value had no fraction at all. AWS S3 always
writes exactly three digits ("...04.560Z"), and clients that parse with a
fixed-width pattern reject anything else. minio-java 8.6.0
(yyyy-MM-dd'T'HH:mm:ss.SSS'Z') throws DateTimeParseException, so roughly
one CopyObject in ten fails on the client even though the copy succeeded.
Two causes:
- xsdDateTime marshalled with "2006-01-02T15:04:05.999999999", which
drops trailing zeros. It now writes UTC with ".000Z".
- CopyObjectResult.MarshalXML had a pointer receiver, but the handlers
pass the result by value, so encoding/xml never called it and fell back
to time.Time's RFC 3339 encoding. It now has a value receiver.
CopyPartResult had no custom marshaller at all; it now uses xsdDateTime.
Follow-up to #8394 / #8398, which truncated these timestamps to
milliseconds but kept the trimmed format.
