post https://sandbox.elabjournal.com/api/v1/storageLayers//reservations
Reservations must be created per compartment. For equipment simply use its main storageLayerID to reserve it. For storage units you can reserve a specific compartment by supplying its storageLayerID.
To create a permanent reservation omit the end date/time or set it to "9999-12-31T00:00:00Z".