Update RequestHandler content and file structure

[kimlundjohansen]

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

Describe the solution you'd like
The content of the request handlers should be like this:

namespace PetStore.PrintLines;

public class GetPrintLineHandler : IGetPrintLineHandler
{
    public async Task<GetPrintLineResult> ExecuteAsync(
        GetPrintLineParameters parameters,
        CancellationToken cancellationToken = default)
    {
	throw new System.NotImplementedException();
    }
}

The files containing the Handler implementation should not be nested in a Handlers folder but in root\Typename\Handlers\

[davidkallesen]

Fixed, see docs:

https://github.com/atc-net/atc-rest-api-generator?tab=readme-ov-file#syntax