[BUG] OpenAPI.yaml generated returns strings without double quotes and "no" string is implicitly interpreted as boolean

Bug Report Checklist

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

Description

openapi.yaml file generated in the project with {{{openapi-yaml}}} like https://github.com/OpenAPITools/openapi-generator/blob/20b8eff6e3dcec5dfe955b5dda1e4b84d8bdce44/modules/openapi-generator/src/main/resources/python-flask/openapi.mustache doesn't use double quotes around string values.
Because in YAML specification, it seems value true/false, yes/no and on/off can be implicitly convert to boolean unless the value have double quotes.
Here the code in PyYAML: https://github.com/yaml/pyyaml/blob/4c2e993321ad29a02a61c4818f3cef9229219003/lib3/yaml/resolver.py#L170-L175

Example: The yaml generated should return - "no" instead of - no to avoid implicit convertion.

openapi-generator version

4.0.3-beta
It can be a regression because it was not present in swagger-codegen

OpenAPI declaration file content or url & Command line used for generation

I am using the online version to generate python-flask server with the following JSON openapi.quote.json.zip

{
  "host": "HOST",
  "info": {
    "description": "Car example",
    "title": "Car API",
    "version": "1.0.0"
  },
  "definitions": {
    "car": {
      "properties": {
        "name": {
          "description": "The name of the car.",
          "maxLength": 255,
          "type": "string"
        },
        "test": {
          "description": "Buggy enum: no becomes False",
          "enum": [
            "no",
            "great",
            "other"
          ],
          "type": "string"
        }
      },
      "required": [
        "name",
        "test"
      ]
    }
  },
  "paths": {
    "/v1/cars": {
      "post": {
        "parameters": [
          {
            "in": "body",
            "name": "body",
            "required": true,
            "schema": {
              "type": "array",
              "items": {
                "$ref": "#/definitions/car"
              }
            }
          }
        ],
        "consumes": [
          "application/json"
        ],
        "responses": {
          "200": {
            "description": "Successfully updated"
          }
        },
        "summary": "Add cars",
        "tags": [
          "Cars"
        ]
      }
    }
  },
  "schemes": [
    "https"
  ],
  "swagger": "2.0"
}

Steps to reproduce

curl -H "Content-type: application/json" -X POST --data-binary @openapi.quote.json http://api-latest-master.openapi-generator.tech/api/gen/servers/python-flask
curl http://api-latest-master.openapi-generator.tech/api/gen/download/298f2e1b-447c-41c1-841f-6544899e3043 -o server.zip
unzip server.zip
cd python-flask-server
cat car_api/openapi/openapi.yaml
python3 -m venv venv
. ./venv/bin/activate
pip install -r requirements.txt
# Run the server
python3 -m car_api

# In other terminal
# "great" value should work and it works: returns "do some magic!"
curl http://localhost:8080/v1/cars -XPOST -H 'Content-type: application/json' -d '[{"name": "car name", "test": "great"}]'

# "fail" value should fail and it fails as expected
curl http://localhost:8080/v1/cars -XPOST -H 'Content-type: application/json' -d '[{"name": "car name", "test": "fail"}]'

# "no" value should work and it fails: returns "detail": "'no' is not one of [False, 'great', 'other']",
curl http://localhost:8080/v1/cars -XPOST -H 'Content-type: application/json' -d '[{"name": "car name", "test": "no"}]'

# Add doubles quotes:
sed -i 's/- \(yes\|Yes\|YES\|no\|No\|NO\|true\|True\|TRUE\|false\|False\|FALSE\|on\|On\|ON\|off\|Off\|OFF\)$/- "\1"/g' car_api/openapi/openapi.yaml

# Run the server with the update applied
python3 -m car_api

# In other terminal
# "no" value should work and it works: "do some magic!"
curl http://localhost:8080/v1/cars -XPOST -H 'Content-type: application/json' -d '[{"name": "car name", "test": "no"}]'

Generated file by openapi generator:

openapi: 3.0.1
info:
  description: Car example
  title: Car API
  version: 1.0.0
servers:
- url: https://HOST/
paths:
  /v1/cars:
    post:
      operationId: v1_cars_post
      requestBody:
        content:
          application/json:
            schema:
              items:
                $ref: '#/components/schemas/car'
              type: array
        required: true
      responses:
        200:
          content: {}
          description: Successfully updated
      summary: Add cars
      tags:
      - Cars
      x-codegen-request-body-name: body
      x-openapi-router-controller: car_api.controllers.cars_controller
components:
  schemas:
    car:
      properties:
        name:
          description: The name of the car.
          maxLength: 255
          type: string
        test:
          description: 'Buggy enum: no becomes False'
          enum:
          - no
          - great
          - other
          type: string
      required:
      - name
      - test
      type: object

Related issues/PRs

Maybe the same error in https://github.com/OpenAPITools/openapi-generator/issues/2870

Suggest a fix

Add double quotes ?

Start with modules/openapi-generator/src/main/resources/python-flask/openapi.mustache and reproduce the issue using the linked openapi.quote.json example and the documented python-flask generation commands. Inspect the generated car_api/openapi/openapi.yaml, then verify that the enum value "no" remains a string and the generated server accepts it without the manual quote substitution.