[BUG][typescript-node] Default enum value in object is generated in a bad way

[GuyGitzMagen]

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

Enum properties containing default value are generated with a bad name that results in build errors.
The default value is set to _, where it should be .. to work correctly:

  export class Fruit {                                                                                                                                                                                                  
      'fruit'?: Fruit.FruitEnum = FruitEnum_Apple; // should be Frute.FruitEnum.Apple                                                                                                                                                                   
  export namespace Fruit {                                                                                                                                                                                              
      export enum FruitEnum {                                                                                                                                                                                           
          Melon = <any> 'melon',                                                                                                                                                                                        
          Apple = <any> 'apple'                                                                                                                                                                                         
      }                                                                                                                                                                                                                 
  }  

openapi-generator version

6.0.0

OpenAPI declaration file content or url

openapi: "3.0.0"
info:
  version: "1.0.0"
  title: "Test default enum value"
paths:
  /eat:
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/Fruit"
      responses:
        200:
          description: "Yummy"

components:
  schemas:
    Fruit:
      type: "object"
      properties:
        fruit:
          type: "string"
          enum: [
              "melon",
              "apple"
            ]
          default: "apple"

Generation Details

I generated the client using:

openapi-generator-cli generate -g typescript-node -i openapi.yml --additional-properties=npmName=example

Steps to reproduce

1. Generate using the command above
2. npm install --inclue=dev
3. npm run build

Related issues/PRs

Suggest a fix

I'm working on a fix that I'll attach shortly.

[GuyGitzMagen]

#12633