retrieve SN that have RG by API GET endpoint and save its body
set null value for the requisitionGroup field
update the given SN by API PUT endpoint
the response should not contain the requisitionGroup field
retrieve SN by API GET endpoint
Bad request with clear error message should be returned when the user tries to remove requisition group from a supervisory node
A user can remove the requisition group from the supervisory node by reassigning that requisition group to another supervisory node
Even if the response from the PUT endpoint tells that the RG has been removed when the SN is retrieved by the GET endpoint the RG is still set to previous value.