[BUG][CSHARP] Issue with readOnly fields and inheritance for csharp-netcore generator

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue? Yes
• Have you validated the input using an OpenAPI validator (example)? Yes
• What's the version of OpenAPI Generator used? latest
• Have you search for related issues/PRs? Yes
• What's the actual output vs expected output? see below
• [Optional] Bounty to sponsor the fix (example)

Description

I found an issue when a schema with a readOnly field is referred to in another Schema
For example:

    Cat:
      type: object
      allOf:
        - $ref: "#/components/schemas/Pet"

    Pet:
      type: object
      properties:
        id:
          type: integer
          format: int64
          readOnly: true

The client generator for csharp-netcore creates a Cat class that inherits Pet (that works fine) and defines a constructor including all the fields present in Pet

        public Cat() : base(id)
        {
        }

There is no constructor in the Pet class with such signature as id is a readOnly field.

openapi-generator version

csharp-netcore

OpenAPI declaration file content or url

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Swagger Petstore
  license:
    name: MIT
servers:
  - url: http://petstore.swagger.io/v1
paths:
  /pets/{petId}:
    get:
      summary: Info for a specific pet
      operationId: showPetById
      tags:
        - pets
      parameters:
        - name: petId
          in: path
          required: true
          description: The id of the pet to retrieve
          schema:
            type: string
      responses:
        '200':
          description: Expected response to a valid request
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Pet"
        default:
          description: unexpected error
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Error"
  /cats/{petId}:
    get:
      summary: Info for a specific cat
      operationId: showCatById
      tags:
        - pets
      parameters:
        - name: petId
          in: path
          required: true
          description: The id of the pet to retrieve
          schema:
            type: string
      responses:
        '200':
          description: Expected response to a valid request
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Cat"
        default:
          description: unexpected error
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Error"
components:
  schemas:
    Pet:
      type: object
      properties:
        id:
          type: integer
          format: int64
          readOnly: true
    Pets:
      type: array
      items:
        $ref: "#/components/schemas/Pet"
    Cat:
      type: object
      allOf:
        - $ref: "#/components/schemas/Pet"
    Error:
      type: object
      required:
        - code
        - message
      properties:
        code:
          type: integer
          format: int32
        message:
          type: string

Command line used for generation

openapi-generator generate -i petstore.yaml -g csharp-netcore -o petstore

Steps to reproduce

• Generate the client from the specification yaml
• Try to build to solution

Suggest a fix

The generator should check for readOnly fields and skip them when referencing the base constructor to avoid this issue

Start by running the provided openapi-generator command with the Pet and Cat schemas, then inspect the generated Cat and Pet constructors. Confirm the generated client builds successfully and that readOnly fields are not passed to a base constructor that does not accept them.