[REQ] Add Ability To Creat Mock APIs For Generated Servers

Is your feature request related to a problem? Please describe.

When doing development of APIs and clients, it is often useful to be able to create Mock API endpoints for testing/validation before putting in lots of effort to implement a real API. This enhancement would allow a generated server to return Mock data based on extension information in the OpenAPI Specification

Describe the solution you'd like

One example would be to use a library like DataFaker or Faker.js in the generated server code to return Mock data based on an x-mock-data attribute on fields in the API Spec.

Describe alternatives you've considered

I have often used Prism and FakeIt to do this, but it would be AWESOME if we could have most server generators integrate this as an option so that you get Mock results until the endpoint is actually implemented.

Additional context

See this article about using DataFaker

The issue names no files, tests, or generator entry points. Start by surveying the generated-server architecture and how OpenAPI extensions are handled; the request would be done when a defined set of server generators can return mock data from an x-mock-data specification extension.