A Google Form which sends all the data, including attachment to a URL of your choice via webhooks.

google_form_webhook.gs

/*
 * Inspired by https://gist.github.com/lifehome/db101c66fe547a8ffbffe10d1bc0b426
 *
 * Please keep the source code updated with this gist at
 * https://gist.github.com/owyongsk/cf36ae0dc9fdb743ae70cb39fe164f8d
 *
 * There's no way to have a gist owned by an organization
 */
 
var webhook_url = "https://your.own/webhook/path";
var webhook_key = "r@nd0mSt1ng";


function onFormSubmit(e) {
  var data = {
    "response": {
      "id": e.response.getId(),
      "timestamp": e.response.getTimestamp(),
      "data": e.response.getItemResponses().map(function(item) { // Maps itemResponses into an array of obj with keys: "key and val"
        return {
          key: item.getItem().getTitle(),
          val: item.getItem().getTitle() == "Receipt" ? getFileBlobsWithFileName(item.getResponse()) : item.getResponse()
        }
      }, this).reduce(function(obj,i){ // Squeezes into one single object
        obj[i.key] = i.val;
        return obj;
      }, {"Email": e.response.getRespondentEmail(), "entropy": Utilities.getUuid()}) // Starting with email and randomly generated entropy as keys
    }
  };

  var string_data = JSON.stringify(data);
  
  var options = {
    method: "post",
    headers: {"Authorization": computeDigestString(string_data, webhook_key)},
    payload: string_data,
    contentType: "application/json; charset=utf-8",
  };

  UrlFetchApp.fetch(webhook_url, options);
};

function getFileBlobsWithFileName(files) {
  return files.map(function(f) {
    var file = DriveApp.getFileById(f);
    return {
      file_name: file.getName(),
      mime_type: file.getMimeType(),
      base64_blob: Utilities.base64Encode(file.getBlob().getBytes())
    }
  }, this);
}

function computeDigestString(payload, secret) {
  var byteSignature = Utilities.computeHmacSha256Signature(payload, secret);
  return Utilities.base64Encode(byteSignature);
}