An Application Programmer Interface is the published set of http endpoints and messages that a service can support. API design and implementation is a rich field of study - here we take a general overview.
Expose access to the Candidates model as a REST endpoint. This involved defining new routes and handlers, which respond simple JSON representations.
Tools like Postman and Insomnia usefully exercise endpoints. However, we can also exercise them problematically, which offers some significant advantages.
Start the development of an API for the donation service, focusing initially on providing access to the Candidates model. Implement the API using simple REST principles.