mod_storage_s3: Remove wrapper and original timestamp from payload (BC) Unpacking the wrapper was already removed in 66986f5271c3 so it was broken already. Just rely on the Last-Modified date instead, it's not going to be accurate if a different timestamp is passed, e.g. with migrations, but that will have to be a future problem. Perhaps the X-Amz-Meta-* can be used?

  * Make groups optional
  * Make groups work with both posixGroup and groupOfNames