api/v5/init bad requests from Mathia/Portal?

[danoswaltCL]

Version where bug was found:
6.0 (possibly before also?)

Describe the bug
There is a itinerant validation error on v5/init that I don't believe was occurring previously before deploying 6. These requests are from Mathia, it might be from the UI side?

The impact is probably not huge, because when I look up these ids, they are generally already init'ed with valid groups and such.

ExperimentUserValidator was changed in v6, we probably should not have touched v5 validator code, but when I look into it, I'm not convinced this should have made a difference.

It's a little weird that a request is being made that looks like this though:

{
    "client_session_id": "6db51e09-8fa6-4757-b1e1-7a717e0a8610",
    "endpoint": "/v5/init",
    "level": "error",
    "message": {
        "endPoint": "/api/v5/init",
        "errorCode": 400,
        "message": "Invalid body, check 'errors' property for more info.",
        "name": "BadRequestError",
        "request": {
            "group": {
                "classId": [
                    ""
                ],
                "schoolId": [
                    ""
                ]
            },
            "id": "638000a9-472f-45a0-9ae7-9ab24cfddc7c"
        },
        "type": "Parameter not in the correct format"
    },
    "request_id": "ab5dd35b-145d-4189-8dc8-8247461af77b",
    "request_method_type": "POST"
}

For whatever reason (a bug in debugging), the logs don't always show there rest of the error, the actual validation error is this:

{
            "property": "group",
            "children": [],
            "constraints": {
                "IsGroupRecord": "The Group is not a valid Record<string, string[]>"
            }
        }