[REQ] Support for arbitrary model property naming

Is your feature request related to a problem? Please describe.

OpenAPI Generator does not currently support arbitrary strings for generated model property names in TypeScript, the OpenAPI specification does not have that limitation.

For example: This is limiting in my use case when working with APIs or specifications that require property names to remain in the kebab-case format.

When using the typescript codegen and setting modelPropertyNaming to original, the property names are incorrectly converted from kebab-case to snake_case.

The following would be valid in TypeScript:

type Example = { 'kebab-case': string };

and so would this (albeit somewhat unorthodox):

type Example = { '|bars|*stars*': string };

Describe the solution you'd like

Add support for arbitrary string property naming in the generated code, particularly for TypeScript, changing how name sanitizing currently works.

Describe alternatives you've considered

• In my case: Manually mapping the snake_case to kebab-case during runtime.
• Post-processing scripts to revert naming changes are possible but add additional development overhead.

Additional Context

It seems that DefaultCodegen sanitizes some specific chars. My understanding of the codebase is limited but perhaps that logic should be language specific as some languages support these arbitrary property names.

Start at DefaultCodegen's name-sanitizing logic and the TypeScript codegen path, focusing on behavior when modelPropertyNaming is set to original. Compare the generated output with the kebab-case and arbitrary-string examples in the issue. Done means valid TypeScript preserves supported arbitrary property names without breaking naming behavior for other generators.