Container with custom mountoptions user_xattr

[jory]

Hello,
How can I mount CT volume (not rootfs but 2nd disk) with mountoptions=user_xattr?
If I set mp0 like this (content is from /etc/pve/lxc/100.conf)

mp0: timemachine-lvm:vm-106-disk-0,mp=/media/TimeMachine,mountoptions=user_xattr,size=900G

I get error

vm 100 - unable to parse value of 'mp0' - format error
mountoptions: value does not match the regex pattern

If I remove mountoptions=user_xattr it starts OK and /media/TimeMachine is accessible. I need to store extended attributes to ext4.
If it's not possible, is it possible to create XFS for 2nd disk of CT?