IdentityServer’s endpoints follow a pattern of abstraction in which a response generator uses a validated input model to produce a response model. The response model is a type that represents the data that will be returned from the endpoint. The response model is then wrapped in a result model, which is a type that facilitates serialization by an implementation of IHttpResponseWriter.
Customization of protocol endpoint responses is possible in both the response generators and response writers. Response generator customization is appropriate when you want to change the “business logic” of an endpoint and is typically accomplished by overriding virtual methods in the default response generator. Response writer customization is appropriate when you want to change the serialization, encoding, or headers of the HTTP response and is accomplished by registering a custom implementation of the IHttpResponseWriter.