[BUG][chsarp-netcore] Underscores and spaces aren't handled properly in enum var names

Created by: sbergen

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

Using underscores or spaces in enum member values does not produce the correct PascalCase output, which would be expected.

openapi-generator version

Reproduces with both 4.3.1 and master

OpenAPI declaration file content or url

A model declaration along these lines will produce issues

"SomeEnum": {
  "title": "Lorem Ipsum",
  "description": "Lorem ipsum", 
  "enum": [
    "foo_bar",
    "bar baz"
  ]
}

Generation Details

Not relevant.

Steps to reproduce

Generate code for any spec with the kind of model described above. It will produce an enum with members named Foobar and Barbaz instead of the expected FooBar and BarBaz.

Related issues/PRs

I will open a PR with a fix and unit tests in a moment.

Suggest a fix

See above.