[1.8] v2 forward compat query API does not support "extern"

Steps to reproduce:
Send request with "extern" property:

POST http://localhost:8086/api/v2/query HTTP/1.1
Content-Type: application/json

{
  "query":"from(bucket: v.bucket)|>range(start:-1d)|>filter(fn: (r) => contains(value: r.object_id, set: v.objectIds))",
  "extern":{
    "type": "File",
    "package": null,
    "imports": null,
    "body": [
      {
        "type": "OptionStatement",
        "assignment": {
          "type": "VariableAssignment",
          "id": {
            "type": "Identifier",
            "name": "v"
          },
          "init": {
            "type": "ObjectExpression",
            "properties": [
              {
                "type": "Property",
                "key": {
                  "type": "Identifier",
                  "name": "bucket"
                },
                "value": {
                  "type": "StringLiteral",
                  "value": "app_dev/autogen"
                }
              },
              {
                "type": "Property",
                "key": {
                  "type": "Identifier",
                  "name": "objectIds"
                },
                "value": {
                  "type": "ArrayExpression",
                  "elements": [
                    {
                      "type": "StringLiteral",
                      "value": "MY_OBJECT_ID"
                    }
                  ]
                }
              }
            ]
          }
        }
      }
    ]
  }
}

Expected behavior:
Get a result back.

Actual behavior:

{"error": "type error 1:93-1:94: undefined identifier \"v\""}

Environment info:

• Docker Image: influxdb:1.8-alpine

Context:
I am experimenting with the new influx js-client (with some custom extensions that enable query variables as described here https://github.com/influxdata/influxdb/issues/16109, see https://github.com/influxdata/influxdb-client-js/pull/178). At my company we are currently using influx v1 with influxql and want to explore a migration strategy towards flux & 2.0 using the new forward compat APIs introduced in 1.8 and query variables would remove the need for string interpolation and extra carefulness to avoid injection attack vectors when crafting queries for influx.