STOW-RS: Query attribute coercion not applied with application/dicom+json

[itayperl]

Describe the bug
When storing an instance via STOW-RS, additional attributes passed via query parameters are ignored when using the multipart/related; type="application/dicom+json" variant.

To Reproduce

echo -ne "\r\n--myboundary\r\nContent-Type: application/dicom+json\r\n\r\n" > mime.metadata.head
echo -ne "\r\n--myboundary\r\nContent-Type: image/jpeg\r\nContent-Location: file1.jpg\r\n\r\n" > mime.jpeg1.head
echo -ne "\r\n--myboundary--" > mime.tail
cat mime.metadata.head metadata.json mime.jpeg1.head file1.jpg mime.tail > metadata+jpeg.mime
curl -X POST -H "Content-Type: multipart/related; type=\"application/dicom+json\"; boundary=myboundary" \
     'http://localhost:8080/dcm4chee-arc/aets/DCM4CHEE/rs/studies?IssuerOfPatientID=foo' --data-binary @metadata+jpeg.mime

Expected behavior
The IssuerOfPatientID attribute should be coerced to foo. This works correctly when uploading a DICOM file using multipart/related; type="application/dicom.

[vrindanayak]

This is not supported as per [DICOM PS3.18 2025b - Web Services - Store Transaction - Query Parameters](https://dicom.nema.org/medical/dicom/current/output/html/part18.html#sect_10.5.1.2