[BUG][Java] Enums with non english language use underscore _ as an identifier

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

The following enum:

                properties:
                  id:
                    type: integer
                    format: int32
                    example: 1
                  name:
                    type: string
                    enum:
                      - هجري
                      - ميلادي
                    maxLength: 7
                    example: هجري

results in:

  public enum NameEnum {
    _("هجري"),
    
    _("ميلادي");

    private String value;

Which in invalid for two reason, 1) underscore is not a valid identifier, 2) The invalid name is repeated.

Solution used by another generator:

  public enum NameEnum {
    _1("هجري"),
    
    _2("ميلادي");

    private String value;

openapi-generator version

6.4

OpenAPI declaration file content or url

Generation Details

spring

Steps to reproduce

Related issues/PRs

Suggest a fix

Reproduce the issue with the supplied OpenAPI enum and the spring generator, then inspect the generated NameEnum output. Confirm that non-English enum values produce valid, unique Java identifiers, and rerun generation to verify the result.