POST /v1.0/1234/instances/1c59bdb8-03b6-4079-a7db-ba92d23a98b3/users HTTP/1.1
User-Agent: python-example-client
Host: openstack.example.com
X-Auth-Token: bb64d788-2dec-4a6b-a670-7151d108cacf
Accept: application/json
Content-Type: application/json