curl --request PUT \
  --url https://{server}/api/assets/{id}/permissions/ \
  --header 'Content-Type: application/json' \
  --cookie sessionid= \
  --data '
{
  "permissions": [
    {
      "flags": 2,
      "subject_type": "user",
      "subject_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a"
    }
  ]
}
'

[
  {
    "subject": {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "subject_type": "<string>",
      "name": "<string>",
      "email": "<string>"
    },
    "flags": 123
  }
]