How do you use the Google Vision API to Scan a Driver's License Barcode From a Server?

Question

We have a project where we are scanning the front and back of a Driver's License for information.

We need the actual scanning to take place server-side and cannot do the actual scan of the driver's license client-side because of reasons. So we therefore need to take a picture, upload it to our server / storage, and have the server perform the image recognition operations.

Google Vision will parse the Strings on the front quite well and we have been successful with pulling the data that way. The problem arises when we move to the back and attempt to scan the PDF417 barcode for information.

Using this code:

https://vision.googleapis.com/v1/images:annotate?key=my_api_key

{
  "requests":[
    {
      "image":{
        "content":"base_64_encoded_image_goes_here"
      },
      "features":[
        {
          "type":"DOCUMENT_TEXT_DETECTION",
          "maxResults":1
        }

      ]
    }
  ]
}

This will successfully return the info we need from the front. With regards to the back and the subsequent PDF417 barcode, I cannot find any documentation or examples for performing this type of scan via the server.

There is plenty of information on client-side ways of doing this, IE:

1) https://developers.google.com/android/reference/com/google/android/gms/vision/barcode/Barcode.DriverLicense

2) https://developers.google.com/vision/android/multi-tracker-tutorial

But nothing for the server / web. We are able to send this photo any way that is needed (base64, Firebase Storage, etc). Does anyone have any ideas as to how this can be done server-side?