narrow_widen_acl: enforce narrowacl in narrow_widen (SEC) Reviewer note: this was sent by the author as a simple bugfix, but can be considered a security patch, since it allows users to access things outside of the ACL, hence the (SEC) prefix. However, this affects the `narrow` extention which is still marked as experimental and has relatively few users aside from large companies with their own security layers on top from what we can gather. We feel (Alphare: or at least, I feel) like pinging the packaging list is enough in this case.

local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed
slicing test passed
issnapshot test passed
findsnapshot test passed