Incorrect `path` attribute on query validation error

Describe the bug

With this query:

query TestQuery($slug: String! = "utay") {
  user(slug: $slug) {
    id
  }
}

This error is returned:

{
  "errors": [
    {
      "message": "Non-null variable $slug can't have a default value",
      "locations": [
        {
          "line": 1,
          "column": 17
        }
      ],
      "path": [
        "query TestQuery"
      ],
      "extensions": {
        "code": "defaultValueInvalidOnNonNullVariable",
        "variableName": "slug"
      }
    }
  ]
}

The issue here is path; it's equal to "query TestQuery" and I think it is not exactly compliant with the graphql spec which expects path to be an array of fields. It is an issue for us because we use a federation router in front of the graphql server and path is invalid for the router in this case.

Versions

graphql version: 2.1
rails version: 7.0.7

Expected behavior

Maybe path shouldn't be set when there's a validation error in the query arguments as some other graphql implementations seem to do that.

(It's a separate topic but some implementations accept default values for non-null variables and it's not clear to me what is the right behavior per the spec.)

Start by reproducing the supplied query against graphql-ruby 2.1 and compare the returned path with the GraphQL error-result specification and Apollo Router expectations. Trace where the validation error's path is assembled, then add a regression check showing that validation errors do not contain the invalid query-operation path.