Changes to Update an equipment downtime by id. This is a full replacement: the window and the whole set of departments and equipment are saved from the request, in request order, so omitting `departments` clears them. The same rules as create apply: the end cannot be earlier than the start, each department must exist and be listed once, and each piece of equipment must be in its department and be listed once for it. The server fills `departmentName` and `equipmentName` from the records.