This release adds handling of two HTTP preconditions: ``If-None-Match: *`` and ``If-Match: *``
To enforce that PUT only creates a resource and does not update it, use ``If-None-Match: *`` header
To enforce that PUT only updates a resource and does not create it use ``If-Match: *`` header
See https://tools.ietf.org/html/rfc7232#section-3.1 for details