add2DoYo.pl builds this holdingsRecord JSON document...
$data = qq[
	{
		"instanceId":"12ef4609-2bca-45ff-bd6d-4ec47aac42c9",
		"permanentLocationId":"96f6675a-9854-49a9-80cc-6e3e2caf1ece"
	}
];
and POSTs it to /holdings-storage/holdings like so:
curl -s -X POST $headers -d '$data' $baseURL/holdings-storage/holdings

note that the JSON that is returned includes a holdingsRecordId...
{
  "id" : "5ada1ed5-d9c4-4fbe-8110-aa3b0b23bbee",
  "_version" : 1,
  "hrid" : "ho00001044034",
  "formerIds" : [ ],
  "instanceId" : "12ef4609-2bca-45ff-bd6d-4ec47aac42c9",
  "permanentLocationId" : "96f6675a-9854-49a9-80cc-6e3e2caf1ece",
  "effectiveLocationId" : "96f6675a-9854-49a9-80cc-6e3e2caf1ece",
  "electronicAccess" : [ ],
  "administrativeNotes" : [ ],
  "notes" : [ ],
  "holdingsStatements" : [ ],
  "holdingsStatementsForIndexes" : [ ],
  "holdingsStatementsForSupplements" : [ ],
  "statisticalCodeIds" : [ ],
  "holdingsItems" : [ ],
  "bareHoldingsItems" : [ ],
  "metadata" : {
    "createdDate" : "2023-10-09T18:34:15.102+00:00",
    "createdByUserId" : "308a01e4-1108-4ea3-aa25-8b1b32cf7643",
    "updatedDate" : "2023-10-09T18:34:15.102+00:00",
    "updatedByUserId" : "308a01e4-1108-4ea3-aa25-8b1b32cf7643"
  }
}