[BUG][OpenAPINormalizer] Specification content lost

[JPPortier]

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?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

OpenAPINormalizer is discarding information from specification when using OAS 3.1 "const" to list enum values based onto oneOf.

Resetting the oneOf, means enums mist and related metadata are lost (e.g. deprecated values).

openapi-generator version

pre-V7.19.0: commit id: 23eff66

OpenAPI declaration file content

    Enum:
      description: xxx
      oneOf:
        - const: 'AAA'
          description: 'AAA description'
        - const: 'BBB'
          description: 'BBB description'
          deprecated: true

Generation Details

Any generator "out of the box"

Steps to reproduce

Use generator with OAS 3.1 file containing following fragment

Related issues/PRs

Issue is coming from OpenAPINormalizer file:

            if (ModelUtils.isIntegerSchema(schema) || ModelUtils.isNumberSchema(schema) || ModelUtils.isStringSchema(schema)) {
                // TODO convert oneOf const to enum
                schema.setOneOf(null);
            }

Suggest a fix

Remove the line resetting the information coming from specifications

[JPPortier]

Fix proposal: #22573