[BUG][KOTLIN] Generated enum does not compile if type mapping is not defined

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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?

Description

The Kotlin generated code does not compile if the type mapping is not explicitly defined, or if it is explicitly set to BigDecimal. By default, the generator uses String to construct the enum.

openapi-generator version

7.17.0

OpenAPI declaration file content or url

openapi: 3.0.0
paths:
  '/':
    get:
      operationId: operation
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ModelWithEnumBigDecimalValue'
components:
  schemas:
    ModelWithEnumBigDecimalValue:
      properties:
        mode:
          type: number
          enum:
            - -1
            - 0
            - 1.1
            - 0.4

this results to this error :

Start by running OpenAPI Generator 7.17.0 with the YAML declaration in the issue and inspect the generated Kotlin enum for ModelWithEnumBigDecimalValue. Compare the output when no type mapping is supplied with the explicit BigDecimal case. Done means the generated Kotlin code for the numeric enum compiles in both cases.