function with argument entered by users?

So I help with a modded network, and one mod has a command to send offline users to spawn (very useful for when something processes wrong and causes the server to hang, as we can send them away from the broken area before they rejoin). However, the mod doesn't have permission nodes and only works for op'd players. 
I want to make a datapack function to run the command as console, with the user being able to add the username, via discord chatlink. The network owner has already set up a way for users to run commands as themselves, so i just need to get the function command set up but i dont know how to add the username argument lol