This user story will need to be rewritten with another endpoint
Functionality of override when item is not loanable already exists with POST /circulation/override-check-out-by-barcode and should be rewritten since current endpoint will not exist any more (https://wiki.folio.org/pages/viewpage.action?pageId=52134914).
Override when item is not loanable will be done through call POST /circulation/check-out-by-barcode.
UI might need to make two calls to the same endpoint in order to complete the action. First - to get the list of checkout errors, second - to override these block after user's decision.