[BUG] csharp generichost generator generates duplicate api methods

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

The generated .NET code seems to generate duplicate API methods.
For example, in GroupsApi.cs:

    public interface IGroupsApi : IApi
    {
        ...
        Task<IGetGroupsIdApiResponse> GetGroupsIdAsync(int id, System.Threading.CancellationToken cancellationToken = default);
        Task<IGetGroupsIdApiResponse?> GetGroupsIdOrDefaultAsync(int id, System.Threading.CancellationToken cancellationToken = default);
        Task<IGetGroupsId_0ApiResponse> GetGroupsId_0Async(int id, System.Threading.CancellationToken cancellationToken = default);
        Task<IGetGroupsId_0ApiResponse?> GetGroupsId_0OrDefaultAsync(int id, System.Threading.CancellationToken cancellationToken = default);
        ...

I don't see any differences between the duplicated API methods.

openapi-generator version

7.9.0

OpenAPI declaration file content or url

Generation Details

csharp.config

{
    "apiName": "FilesComApi",
    "library": "generichost",
    "netCoreProjectFile": true,
    "nullableReferenceTypes": true,
    "optionalAssemblyInfo": true,
    "packageName": "Files.Com.Core",
    "targetFramework": "net8.0",
    "sourceFolder": "src"
}

Steps to reproduce

• Create csharp.config file
• Execute the following:

nvm install latest
nvm use latest
npm install -g npm@latest
npm install @openapitools/openapi-generator-cli -D
curl -o filescom-v1.json https://app.files.com/api/rest/v1/swagger_doc.json
npx @openapitools/openapi-generator-cli generate -i .\filescom-v1.json -o .\generated -g csharp -c csharp.config

Build

cd generated
dotnet new globaljson --sdk-version 8.0.400 --roll-forward feature
dotnet build

Related issues/PRs

#19626

Suggest a fix

Start with the generated GroupsApi.cs and csharp.config, then reproduce the duplicate methods using the provided OpenAPI document and generator command. Compare the GetGroupsIdAsync and GetGroupsId_0Async variants, and confirm the fix by generating the client again and running dotnet build without duplicate API methods.