post https://{region}.mixpanel.com/groups#group-batch-update
Send a batch of group profile updates. Instead of sending a single JSON object as the data query parameter, send a JSON list of objects as the data parameter of an application/x-www-form-urlencoded POST or GET request body.
Refer to the respective group profile update commands ($set, $set_once, $add, $union, $remove, $unset, and $delete) on syntax for their parameters.