Add Support For FastEndpoints

[KyleMcMaster]

We already have support for Minimal API results so it would be awesome to see what work is needed to also support FastEndpoints like we do for Controllers/APIEndpoints. If any code is needed it could probably be added to the AspNetCore package unless we would like to add an Ardalis.Result.FastEndpoints package

[itsoli91]

FastEndpoint already has a SendResultAsync() to send any IResult instance produced by the Results static class in Minimal APIs. So simply you can call something like this:
await SendResultAsync(result.ToMinimalApiResult());
More info: https://fast-endpoints.com/docs/misc-conveniences#send-methods

[ardalis]

It might need something like this:

static class ArdalisResultsExtensions
{
    public static async Task SendResponse<TResult, TResponse>(this IEndpoint ep, TResult result, Func<TResult, TResponse> mapper) where TResult : Ardalis.Result.IResult
    {
        switch (result.Status)
        {
            case ResultStatus.Ok:
                await ep.HttpContext.Response.SendAsync(mapper(result));
                break;

            case ResultStatus.Conflict:
                await ep.HttpContext.Response.SendAsync(result.Errors, 409);
                break;

            case ResultStatus.Invalid:
                result.ValidationErrors.ToList().ForEach(e =>
                    ep.ValidationFailures.Add(new(e.Identifier, e.ErrorMessage)));

                await ep.HttpContext.Response.SendErrorsAsync(ep.ValidationFailures);
                break;
        }
    }
}