[python-nextgen] Inconsistent enum naming

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?
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Description

There is a enum naming inconsistence between the python-nextgen generators and others (php, js, ts, go, ruby, java, .net), for example from this enum:

type: string
title: EventType
enum:
  - it.test.company.create
  - it.test.company.update
  - it.test.user.create
  ...

the other generators generate enum keys like CompanyCreate, CompanyUpdate and so on, while the python-nextgen instead generated keys are IT_DOT_COMPANY_DOT_CREATE, IT_DOT_COMPANY_DOT_UPDATE...

It seems like the common part of all the options (in this case it.test) does not get stripped, and special chars get transformed in words instead of removed, it's true that it's more similar to the options I specified in the actual openapi but I think the behaviour of the other generators is way better in the end, other than the fact that it will be better to have consistency across all the generators.

Suggest a fix

What I would expect from the example openapi I put above is an enum with keys COMPANY_CREATE, COMPANY_UPDATE and USER_CREATE.

openapi-generator version

6.5.0

Related issues/PRs

https://github.com/OpenAPITools/openapi-generator/pull/14869

Start by reviewing the python-nextgen generator and the related pull request #14869, then compare its enum naming with the other generators described in the issue. Reproduce the provided OpenAPI enum example and verify that generated keys omit the shared prefix and represent the expected COMPANY_CREATE, COMPANY_UPDATE, and USER_CREATE names.