[Swift4] Schema with inner objects with required properties are marked optional

Description

See examples below

Swagger-codegen version

3.0.3

Swagger declaration file content or url

    Person:
      required:
        - name
      type: object
      properties: 
        name:
          type: object
          required:
            - first
            - last
          properties:
            first: 
              type: string
            last:
              type: string

Generates:

public struct Person: Codable {


    public var name: PersonName
    public init(name: PersonName) { 
        self.name = name
    }

}

public struct PersonName: Codable {


    public var first: String?

    public var last: String?
    public init(first: String?, last: String?) { 
        self.first = first
        self.last = last
    }

}

It's unexpected that first and last name are optional since they are marked required. On the other hand, using refs it works:

    Person:
      required:
        - name
      type: object
      properties: 
        name:
          $ref: '#/components/schemas/Name'
    Name:
      required:
        - first
        - last
      type: object
      properties:
        first: 
          type: string
        last:
          type: string

Generates:

public struct Person: Codable {


    public var name: Name
    public init(name: Name) { 
        self.name = name
    }

}

public struct Name: Codable {


    public var first: String

    public var last: String
    public init(first: String, last: String) { 
        self.first = first
        self.last = last
    }

}

Command line used for generation

swagger-codegen generate -i test.yaml -l swift4 -Dmodels

Start with the Swift4 model generation entry point used by swagger-codegen generate -i test.yaml -l swift4 -Dmodels, comparing inline nested objects with equivalent $ref schemas. Done means required nested properties such as first and last are generated as non-optional Swift properties in the inline case as well.