Build an OData service for the library with SAP CAP: CDS model, initial data, validation with before and a virtual field with after. All in TypeScript and tested with real requests.
Build a SEGW service on a Z table where GET is served by a CDS view through SADL and POST goes through a BOPF business object, with validations, OData messages and an action.
Publish the annotated CDS as an OData service, generate a Fiori Elements app, deploy it to the ABAP repository and bring it to the Launchpad with catalog, tile, target mapping and role.