POST /v3/instruments/:id/net-asset-values

Append one NAV observation to a private-market-fund instrument.

Path params:
  id (required) — Instrument identifier (Mongo ObjectID).

Request:
{
  "data": {
    "type": "net-asset-value",
    "attributes": {
      "officialDate":  "string, ISO 8601 (required)",
      "effectiveDate": "string, ISO 8601 (optional) — null → defaults to officialDate",
      "value":         "number (required) — in fund currency"
    }
  }
}

Response (201 Created):
{
  "data": {
    "id": "string",
    "type": "net-asset-value",
    "attributes": {
      "officialDate":  "ISO 8601 date",
      "effectiveDate": "ISO 8601 date or null",
      "value":         "number"
    }
  }
}