Permission denied when changing permissions on a directory mounted and squashed

Hello,

I would like to mount, as a regular user (not in a namespace or mapped uid/gid), a directory normally owned by root and have it writable, but also changing the owner to my regular user as well. I thought `-o squash_to_uid=myuid` was about to do the trick, but it didnt:

```
mkdir upper work mounted
fuse-overlayfs \
-o lowerdir=/opt/foobar \
-o upperdir=$PWD/upper \
-o workdir=$PWD/work \
-o squash_to_uid=`id -u` \
-o squash_to_gid=`id -g` \
mounted
```

The mounted is owned by me and I can write to it, but I cannot change ownership:

```
$ touch mounted/test
$ ls -l mounted
-r-xr-xr-x akiross akiross foo
-r-xr-xr-x akiross akiross test
-rwxrwx akiross akiross test

$ chmod 755 mounted/foo
chmod: changing permissions of 'mounted/foo': Permission denied
```

I thought overlayfs would save file metadata, and modifications to files, in the `upper` directory, so what I'm trying to do sounds legit, but I might be missing something.

Is it possible to achieve this with unprivileged user?

Start by reproducing the unprivileged fuse-overlayfs command using the lowerdir, upperdir, workdir, squash_to_uid, and squash_to_gid options shown in the report. Trace the permission-changing path for mounted/foo and determine whether the requested ownership and chmod behavior is supported; done means the behavior is fixed or clearly documented.

Written by the indexing model from the issue text.