Script or droplet to handle opening of specific file type, is it possible?

Hello, I'm new to the MacOS world and have an urgent need to support my Mac users for a web application. Here is what I need;

A user opens a file of specific type, extension "message.hef". For the most part the file is received as an email attachment.

A script or droplet gets called by the system with a path to the file

The script opens Safari with a pre-determined URL and waits for the user to signin and the page to load.

The script sets the form "file" value to the file path (or simulate a drag&drop) and issues a post to the web server to upload the file for processing

I'm currently providing the users with a desktop .webloc file that they open safari on the page and lets the user to drag&drop the file. But, the user experience for them is unacceptable and simply want to click on the file.

Thanks in advance for your help and support.