Fix charset to UTF-8 in part attachments. The forward and recall
commands fetch message parts with the go-message package which decodes
to UTF-8. Hence, we should set the charset of the part attachment to
utf-8 and not just copying over the one from the original message.
Reported-by: Bence Ferdinandy <bence@ferdinandy.com>
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>