Create a custom field

Example request

{
  "name": "some string",
  "position": 0,
  "permission": "1,2,3",
  "is_active": true,
  "object": "customer",
  "can_customer_view": true,
  "field_widget_id": 1,
  "settings": {
    "field_instance_id": 1,
    "allowed_values": [
      "value_1",
      "value_2"
    ],
    "default_value": "value_1"
  }
}