public function handle($data)
 {
     $this->validate_request(["group-name"]);
     $groupname = $data->{"group-name"};
     $displayname = $groupname;
     if (isset($data->{"display-name"})) {
         $displayname = $data->{"display-name"};
     }
     if (GroupBackend::group_exists($groupname)) {
         throw new EndpointExecutionException("Group with name already exists", ["group-name", $groupname]);
     }
     // Add the group to the database
     $group = GroupBackend::create_group($groupname, $displayname);
     // Return the new user to the client
     return ["group" => $group->toExternalForm()];
 }