[BUG][TypeScript] Make ExtendedCodegenOperation and ExtendedCodegenModel public?

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

We have a TypeScript client codegen that inherits from TypeScriptFetchClientCodegen and overrides
the fromModel and fromOperation methods. In previous releases, these methods were inherited directly from DefaultCodegen through TypeScriptFetchClientCodegen. However, version 5.2.1 and above of TypeScriptFetchClientCodegen overrides these methods and returns ExtendedCodegenOperation and ExtendedCodegenModel, which breaks our code generator because the classes ExtendedCodegenOperation and ExtendedCodegenModel have package access. Is there a reason why these classes were given package access? Could they be made public?

openapi-generator version

5.2.1

Suggest a fix

Make the ExtendedCodegenModel and ExtendedCodegenOperation classes public. In fact make all the Extended* classes public.

Start by locating ExtendedCodegenOperation and ExtendedCodegenModel in the Java codegen sources and tracing their use from TypeScriptFetchClientCodegen's fromOperation and fromModel methods. Check whether the affected Extended* classes are intended for external inheritance, then verify that a TypeScript client generator can use the returned types; the issue is resolved when the types are publicly usable without breaking generation.