{
  "type": "object",
  "required": ["id", "type", "attributes"],
  "properties": {
    "id": { "type": "integer" },
    "type": { "type": "string" },
    "attributes": {
      "type": "object",
      "required": ["email"],
      "properties": {
        "email": { "type": "string" },
        "username": {
          "oneOf": [
            { "type": "string" },
            { "type": "null" }
          ]
        }
      },
      "additionalProperties": false
    }
  },
  "additionalProperties": false
}