Updates an Experience Group record.

Note: When updating an existing Experience group you have the option of including either a set of nested Experiences or groups, not both, that belong to the new group. As a result, a prioritization record will be created in addition to each individual group or Experience itself being updated with the proper parent_group_id value. Likewise, passing an empty array WILL REMOVE the ownership from the existing children. When no change is intended for nested Experiences or groups you should pass no value or null for both experiences and child_groups.