GET /v3/instrument-holdings/reporting-entities/:id

Get per-instrument holding values for a reporting entity over a date
range. Always includes `unitsInHolding`.

Path params:
  id (required) — Reporting-entity identifier.

Query params:
  fromDate (required) — First date (inclusive, ISO 8601).
  toDate   (required) — Last date  (inclusive, ISO 8601).

Response (200 OK):
{
  "data": [
    {
      "id": "string",
      "type": "instrument-holding",
      "attributes": {
        "date":           "ISO 8601 date",
        "ccyCode":        "string — ISO 4217",
        "marketValue":    "number",
        "unitsInHolding": "number"
      },
      "relationships": {
        "reportingEntity":         { "type": "reporting-entity", "id": "string" },
        "portfolio":               { "type": "portfolio", "id": "string" },
        "instrument":              { "type": "instrument", "id": "string" },
        "depository":              { "type": "depository", "id": "string (optional)" },
        "instrumentClass":         { "type": "instrument-class", "id": "string (optional)" },
        "instrumentClassDetailed": { "type": "instrument-class-detailed", "id": "string (optional)" }
      }
    }
  ]
}