Contact groups have been deprecated. Use Contact Lists instead.
Example Contact Group Object
{
"_links": {
"self": "https://api2.frontapp.com/contacts/grp_55c8c149",
"related": {
"contacts": "https://api2.frontapp.com/contact_groups/grp_55c8c149/contacts",
"owner": "https://api2.frontapp.com/teams/tim_55c8c149"
}
},
"id": "grp_55c8c149",
"name": "Customers",
"is_private": false
}