Support for ServerObject and ServerVariableObject

[raveclassic]

• we should support flexible server path configuration:
  • https://swagger.io/docs/specification/api-host-and-base-path/
  • https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#server-object-example
  • https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#server-variable-object