Add endpoint examples defined in the spec to API servers

[wing328]

Description

Similar to what we've done for SpringMVC generator, we want to add support of endpoint examples defined in the spec to the auto-generated server stubs.

Ref: #5411

Endpoint example support in the server generators:

• C# (NancyFx, ASP.net Core)
• Elixir
• Erlang
• Go
• Haskell Servant
• JavaScript/NodeJS
• Java (MSF4J, Spring:white_check_mark:, Undertow, JAX-RS: CDI, CXF, Inflector, RestEasy)
• PHP (Lumen, Slim, Silex, Zend Expressive)
• Python Flask
• Ruby (Sinatra, Rails)
• Scala Finch
• Scala Scalatra

Suggest a Fix

#5411 is a good reference. If anyone wants to contribute to this task, please reply to let us know. Thank you.