Query what groups a user is in without shortcode?

I’m trying to alert another one of my systems when a user’s groups change. I used the ‘profile_update’ action of WordPress to send a post call to my other system when someone updates their profile.

I’d like to send just the group names as an array with the post call, but I can’t find a function or anything other than a shortcode that does this. Any ideas on how I could achieve that?

https://www.ads-software.com/plugins/groups/