[BUG][SWIFT4] Inherited enumerations are not being generated correctly

Description

Whenever a definition is inheriting enumeration fields (using allOf), these end up being generated without any options.

public enum Status: String, Codable {
}

Those same enumerations are being generated correctly on the original definition.

Our spec is still using swagger 2.0.

openapi-generator version

Happening on v3.3.4. Was using swagger-codegen before and did not have this issue.

OpenAPI declaration file content or url

ParentObject:
    type: object
    required:
      - id
      - status
    properties:
      id:
        type: string
      status:
        type: string
        enum:
          - generate
          - activate
          - suspend
          - refund
          - expire
          - burn
  NamedChildObject:
    allOf:
      - $ref: '#/definitions/ParentObject'
      - type: object
        properties:
          name:
          type: string

Using the example above, NamedObject will look like:

public struct NamedChildObject: Codable {

    public enum Status: String, Codable {
    }
    public var _id: String
    public var status: Status

    public init(_id: String, status: Status) {
        self._id = _id
        self.status = status
    }

    public enum CodingKeys: String, CodingKey { 
        case _id = "id"
        case status
    }
}

Reproduce the issue with the supplied Swagger 2.0 declaration using openapi-generator v3.3.4, then inspect Swift 4 generation for inherited properties handled through allOf. Done when NamedChildObject.Status contains the inherited enum options while the original definition continues to generate correctly.