Gets a group by ID.
The getGroup() function returns a Promise that resolves to a group whose ID matches the given ID.
Note: For SECRET groups, only site admins, group admins, and group members can see a group and its content. However, if the suppressAuth option is set to true, all permissions are overwritten, and all site members (including non-group members) can see a group and its content.
ID of requested group.
Authorization options.