Deluge: How to get the application/octet-stream response using the 'invokeUrl' method?

I'm in the middle of setting up a 'scheduled email notifications' Flow, but I am unsure if this is the best path to do it. So alternate title for this post is "What's the best setup for emailing an inventory feed to your customers."

The setup is simple, I added a scheduled trigger and connected it to a function that 1. requests an excel file from SharePoint REST API, 2. fetches all customers with "Inventory Feed" field selected, and 3. sends an email with the file from SharePoint attached.

Here's a snippet

void send_inventory_feed_to_email()
{
// 1. requests an excel file from SharePoint Rest API
token = get_sharepoint_token();
url = "https://domain.sharepoint.com/sites/Team/_api/Web/GetFolderByServerRelativePath(decodedurl='/sites/SomeFolder')/Files('Inventory.xlsx')/$value";
// main issue - 'excel_file_from_sharepoint' returns "1667937294042.octet-stream" - a string instead an actual octet-stream content
excel_file_from_sharepoint = invokeurl
[
url :url
type :GET
headers:{"Authorization":"Bearer ".concat(token),"Content-Type":"application/octet-stream","Accept":"application/octet-stream"}
];
// 2. fetches all customers with "Inventory Feed" field selected
for each subscriber in get_inventory_feed_subscribers()
{
// I'm not sure if this is the right way of using the Upload attachment API, so correct me if I'm wrong
attachment = invokeurl
[
url :"https://mail.zoho.com/api/accounts/xxxxxxxxxxxxxxxxxxxx/messages/attachments"
type :POST
parameters:{"fileName":"Inventory Feed.xlsx","file":excel_file_from_sharepoint}
content-type:"multipart/form-data"
];
attachment = attachment.get("data").get(0);
//3. sends an email with the file from SharePoint attached
email = invokeurl
[
url :"https://mail.zoho.com/api/accounts/xxxxxxxxxxxxxxxxxxxx/messages/messages"
type :POST
parameters:{"attachments":{"storeName":attachment.get("storeName"),"attachmentPath":attachment.get("attachmentPath"),"attachmentName":attachment.get("attachmentName")}}
];
}
}