Update an existing assignment

Example request

{
  "active": true,
  "provisioned": true,
  "validated": true,
  "description": "Short description here",
  "owner": "jsbach",
  "qinq": 1,
  "wipe": true,
  "ccuser": [
    "edroste",
    "kgodel"
  ],
  "cloud_id": 12,
  "vlan_id": 12
}