This endpoint provides Quiescent Physical Notification data received from NGESO. It returns the data valid for a single settlement period. Quiescent Physical Notifications describe the MW levels to be deducted from the Physical Notification of a BM Unit to determine a resultant operating level. The settlement period to query can be specified as a date and settlement period, or as a datetime which will resolve to the settlement period that time falls within. If a settlement period is provided, it will take precedence over the time portion of the datetime.