The "changedSince" query parameter does not work

Hi, I am currently using the test environment to develop integration with Tripletex and it seems the changedSince field in the query parameters is ignored. Tested so far the endpoints for Customer and Supplier.

Testing with Postman or directly at https://api-test.tripletex.tech/v2-docs/ return all entity records.

GET https://api-test.tripletex.tech/v2/customer?changedSince=2030-09-09T18:00:00Z&fields=changes

Response: 
{
    "fullResultSize": 193,
    "from": 0,
    "count": 193,
    "versionDigest": "'If-None-Match' header not specified",
    "values": [
        {
            "changes": [
                {
                    "employeeId": 11889083,
                    "timestamp": "2025-03-12T15:09:57+01:00",
                    "changeType": "CREATE"
                },
                {
                    "employeeId": 11890724,
                    "timestamp": "2025-04-30T09:35:45+02:00",
                    "changeType": "UPDATE"
                }
            ]
        },
        {
            "changes": [
                {
                    "employeeId": 11889083,
                    "timestamp": "2025-03-12T15:09:57+01:00",
                    "changeType": "CREATE"
                }
            ]
        },
        {
            "changes": [
                {
                    "employeeId": 11889083,
                    "timestamp": "2025-03-12T15:09:57+01:00",
                    "changeType": "CREATE"
                }
            ]
        },
	...
    ]
}

Start by reproducing the GET requests in Postman or the test API documentation for the Customer and Supplier endpoints, using the shown changedSince value and fields=changes. Trace where these endpoints process changedSince, then verify that responses exclude records changed before the supplied timestamp.