[BUG] [JAVA] Java generation of 'extra' class with allOf

Created by: renskesterrenburg

Description

I am using the pet store example to create java classes with inheritance. In the newest release (4.0.1) I found a bug. When I generate code with the OpenApi declaration file it generates an extra class.

The class 'CatAllOf' I did not expect. It looks the same as 'Cat' except that it does not extends Pet.

OpenAPI declaration file:

openapi: 3.0.1
info:
  title: Article Event
  description: 'Article Event schema'
  version: 1.0.0
paths:
  /:
    get:
      responses:
        200:
          description: OK
          content: {}
components:
  schemas:
    TextChunk:
      type: object
      discriminator:
        propertyName: textChunkType
      properties:
        parent:
          type: string
    Dog:
      allOf: 
      - $ref: '#/components/schemas/TextChunk'
      - type: object
    Cat:
      allOf:
      - $ref: '#/components/schemas/TextChunk'
      - type: object
        properties:
          bark:
            type: string

openapi-generator version I used the gradle plugin with version 4.0.1.

older version I tested the same thing in the version 4.0.0-beta3 and there I did net see the 'extra' class. In other words, I got the expected behavior. It seems the bug was introduced with the latest release.