[BUG] CodegenModel allVars doesn't contain all variables

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

CodegenModel.allVars does not contain all variables.

openapi-generator version

6.0.1

OpenAPI declaration file content or url

openapi: 3.0.1
info:
  version: 1.0.0
  title: Example
  license:
    name: MIT
servers:
  - url: http://api.example.xyz/v1
paths:
  /person:
    post:
      operationId: create
      requestBody:
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/AbstractPerson"
        description: order to create
        required: true
      responses:
        '200':
          description: OK
components:
  schemas:
    AbstractPerson:
      type: object
      discriminator:
        propertyName: gender
      properties:
        name:
          type: string
      required:
        - name
    Male:
      type: object
      allOf:
        - $ref: "#/components/schemas/AbstractPerson"
      properties:
        footballs:
          type: integer
    Female:
      type: object
      allOf:
        - $ref: "#/components/schemas/AbstractPerson"
      properties:
        high-heels:
          type: integer
      required:
        - high-heels

Generation Details

I used a AbstractKotlinCodegen, e.g. KotlinClientCodegen.

Steps to reproduce

use openapi def and add

// allVars
{{#allVars}}
    // {{name}}
{{/allVars}}
// requiredVars
{{#requiredVars}}
    // {{name}}
{{/requiredVars}}
// optionalVars
{{#optionalVars}}
    // {{name}}
{{/optionalVars}}

to data_class.mustache OR add a breakpoint in AbstractKotlinCodegen.fromModel

Related issues/PRs

Suggest a fix

Start with AbstractKotlinCodegen.fromModel and reproduce the issue using the OpenAPI declaration in the report. Add the diagnostic blocks to data_class.mustache, compare allVars with requiredVars and optionalVars for the inherited schemas, and confirm that all expected variables are present.