Docs for exposing REST API of a Model with no custom classes

[bajtos]

Documentation for the feature From model definition to REST API with no custom repository/controller classes #2036

Acceptance criteria

• Docs for application developers consuming this feature. Describe the new CLI command, how to use controller/repositories contributed by extensions, what model config options are available.

• Docs for extension developers building custom controller/repository classes. Explain what API contract the custom controller/repository class must implement, show how the component must export the classes so that they can be picked by the Booter.