[BUG][DefaultCodegen] OneOf with discriminator for referenced object with allOf

[Axent96]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Warninng: [main] WARN o.o.codegen.DefaultCodegen - 'GeneralProduct' defines discriminator 'type', but the referenced schema 'HomeProduct' is incorrect. type is missing from the schema, define it as required and type string

openapi-generator version

7.7.0

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: test
  description: Test
  version: "2.0"
servers:
  - url: 'https://example.com'
security:
  - APIKeyHeader: []
paths:
  /products/{identifier}:
    get:
      tags:
        - Product Item
      summary: Get single product
      parameters:
        - name: identifier
          in: path
          required: true
          schema:
            type: string
          example: "100001951"
          description: The product identifier
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/GeneralProduct'
components:
  schemas:
    GeneralProduct:
      type: object
      oneOf:
        - $ref: '#/components/schemas/HomeProduct'
        - $ref: '#/components/schemas/InternetProduct'
      discriminator:
        propertyName: type
        mapping:
          home: '#/components/schemas/HomeProduct'
          internet: '#/components/schemas/InternetProduct'
    HomeProduct:
      allOf:
        - $ref: "#/components/schemas/Product"
        - type: object
          required:
            - newField
          properties:
            newField:
              type: string
    InternetProduct:
      allOf:
        - $ref: "#/components/schemas/Product"
        - type: object
          required:
            - extraField
          properties:
            extraField:
              type: string
    Product:
      type: object
      required:
        - productId
        - name
        - type
      properties:
        productId:
          type: string
        name:
          type: string
        type:
          $ref: '#/components/schemas/AboType'
    AboType:
      type: string
      enum:
        - "internet"
        - "home"

Generation Details

java -jar codegen/openapi-generator-cli-7.7.0.jar generate -i ./api.json -g php --invoker-package=Test\Main --api-package=Client --model-package=Models --additional-properties=variableNamingConvention=camelCase --additional-properties=disallowAdditionalPropertiesIfNotPresent=false --additional-properties=legacyDiscriminatorBehavior=false -o /tmp/

Steps to reproduce

Generate a library

[MoellJ]

I think I'm experiencing the same issue.
I'm currently unsure if this example is spec conform or if using discriminator is a special case where the inheriting schema needs to contain the discriminator field directly an can not rely on allOf with a $ref. (Would be weird if this wasn't allowed though)

(The spec I'm working with is created via https://github.com/springdoc/springdoc-openapi .)