Add Missing API HttpResponse.HeadersWritten

[Clounea]

Summary

Our repo uses HttpResponse.HeadersWritten which is not supported by ASP.NetCore and this adapters.
I want to ask if there is equivalent and if there is plan to add them to adapter.

Motivation and goals

We need migrate code (an API in Sharepoint) to ASP.NetCore and we find that the APIs are not supported by ASP.NetCore.

In scope

HttpResponse.HeadersWritten

I think Microsoft.AspNetCore.Http.HttpResponse.HasStarted Could implement it.
https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.httpresponse.hasstarted?view=aspnetcore-8.0#Microsoft_AspNetCore_Http_HttpResponse_HasStarted
https://stackoverflow.com/questions/55119289/response-headerswritten-in-asp-net-core-2

Examples

// if headers is sent, can't proxy
bool canProxy = !context.Response.HeadersWritten;

[twsouthwick]

Using HttpResponse.HasStarted seems reasonable to me. @Tratcher any thoughts?

[Tratcher]

Yes, those seem to map.

[twsouthwick]

@Clounea happy to take a PR for this