[Swift] Empty Struct Generated Which Should be a Typealias

Description

swagger-codegen does not create a correct Swift representation for a simple Model (from a schema definition) which would be ideally generated as a Swift typealias.

Swagger-codegen version

This is the current version used in website: 3.0.10 (current tag)
openapi: 3.0.0

Swagger declaration file content or url

The following yaml snippet (openapi: 3.0.0) shows how the model is defined in section components/schemas:

components:
  schemas:
    Id:
      type: string
      format: uuid
      example: d290f1ee-6c54-4b01-90e6-d701748f0851
      description: A unique identifier.

This is basically a type String which has a special format (UUID).

Command line used for generation

The code generator has been invoked from the Export feature from the website app.swaggerhub.com:

Export -> Client SDK -> swift4

Expected

Swift:

    typealias Id = String

Actual

//
// Id.swift
//
// Generated by swagger-codegen
// https://github.com/swagger-api/swagger-codegen
//

import Foundation

/** An ID uniquely identifying the object. */
public struct Id: Codable {


}

As you can see, this is an empty struct and can not be used in any way.

Steps to reproduce

Well, this would require to setup a basic swagger spec and include the schema in the components section, then generate the code.

Related issues/PRs

Almost the same issue, just differently generated code containing no usable properties, and this was "swagger 2.0":
https://github.com/swagger-api/swagger-codegen/issues/6946

Suggest a fix/enhancement

My preferred representation in Swift:

    typealias Id = String

Hint: a quick check for the language Kotlin showed that there is no issue like this as in Swift. For Kotlin, actually a typealias will be generated.

Reproduce the OpenAPI 3.0 schema with the website's Export → Client SDK → swift4 entry point, then trace the Swift generator output for the Id model. Done means the generated Swift representation is a usable typealias to String rather than an empty struct.