No Way to Bulk Add Users to a Group Without Writing a Ton of JSON?

I'd like to add a bunch of users to a group. I have the group ID, and the user IDs, but the only way to pass this information, seems to be by using the group_memberships endpoint, and writing a JSON statement per user you want to update. This is not ideal, especially if you're using Postman and want to update 100+ users to have membership to the same group. It's a lot of tedious copy and pasting and formatting (or tedious 'writing a script to do the copy/pasting'). I'd love to be able to plug in a list of user ID as a parameter, and a group ID as a parameter, and be able to update them that way, instead of writing a custom body every single time. Am I missing something, or is this really not possible?