Update Units of Measurement Settings

Update settings for [units of measurements](https://support.bigcommerce.com/s/article/Store-Settings?language=en_US#physical). The endpoint does not support partial updates. Provide all fields to update global or channel-level settings. Create channel-level settings, or overrides for a channel, using the `channel_id` query parameter. To delete overrides for a channel, supply `null` as a value for all fields. A channel then inherits global values. The endpoint does not support 'null' as ...