[BUG] Enums with numeric double values are passed to the models as strings, not numbers

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?

See this file for debug output showing incorrect model value generation.

output.txt

Description

    DoubleChoice:
      type: number
      format: double
      enum:
        - 6.4
        - 9.9

This OpenAPI model should generate value: "6.4" but instead generates value: "'6.4'" with additional single-quote string markers.

Output, according to --global-property debugModels:

{
      "openApiType" : "DoubleChoice",
      "allowableValues" : {
        "enumVars" : [ {
          "name" : "number6Period4",
          "isString" : false,
          "value" : "'6.4'"
        }, {
          "name" : "number9Period9",
          "isString" : false,
          "value" : "'9.9'"
        } ],
        "values" : [ 6.4, 9.9 ]
      },
   /// rest omited
}

Meanwhile, integer types generate correctly:

{
      "openApiType" : "IntChoice",
      "allowableValues" : {
        "enumVars" : [ {
          "name" : "number64",
          "isString" : false,
          "value" : "64"
        }, {
          "name" : "number99",
          "isString" : false,
          "value" : "99"
        } ],
        "values" : [ 64, 99 ]
      },
/// rest omitted 
}

openapi-generator version

436a3e0744a2ce8208a7c3b8116fca6e7195143a

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  version: "1.1"
  title: Double Values Incorrect
servers:
  - url: "localhost"
    variables:
      host:
        default: localhost
paths:
  /getItem:
    get:
      operationId: getItem
      description: "Should return enum type of doubles"
      responses:
        "200":
          description: "get enum type of doubles"
          content:
            application/json:
              schema:
                $ref: "#components/schemas/NonStringEnums"


components:
  schemas:


    NonStringEnums:
      type: object
      description: "Has non-string enum types"
      required:
        - strChoice
        - intChoice
      properties:
        strChoice:
          $ref: "#/components/schemas/StrChoice"
        intChoice:
          $ref: "#/components/schemas/IntChoice"
        doubleChoice:
          $ref: "#/components/schemas/DoubleChoice"
        boolChoice:
          $ref: "#/components/schemas/BoolChoice"
    
    
    StrChoice:
      type: string
      enum:
        - FirstChoice
        - SecondChoice
    IntChoice:
      type: integer
      enum:
        - 64
        - 99
    DoubleChoice:
      type: number
      format: double
      enum:
        - 6.4
        - 9.9
    BoolChoice:
      type: boolean
      enum:
        - true
        - false

Steps to reproduce

java -jar modules\openapi-generator-cli\target\openapi-generator-cli.jar generate -g dart -i .\incorrect_double_enum.yml -o incorrectDoubles --global-property debugModels > output.txt

Suggest a fix

Generate doubles choices like int choices, remove the quotation marks.

Reproduce the issue with the provided OpenAPI YAML and Dart generation command using --global-property debugModels. Trace how the generator creates enumVars values; done means the debug output represents 6.4 and 9.9 without added single-quote markers, matching the integer enum behavior.