Move the SseResponseStreamTransport out of sample

[halter73]

TODO:

• Add tests
  • We now have some integration test coverage, because this is now used by the SseServerIntegrationTests.
• Add logging I decided against adding logging since logging could be added by the creator of the transport like the ASP.NET Core sample or the HttpListenerSseServerTransport as demonstrated by this PR.
• Use it in the HttpListenerSseServerTransport Done

I'm working on these things now, but if we like the API shape, I think we can merge it as-is to let people try it out and do the TODOs as follow ups.

[stephentoub]

Use it in the HttpListenerSseServerTransport

Where is this being done?

[PederHP]

Use it in the HttpListenerSseServerTransport

Where is this being done?

I assume it's where HttpListenerSseServerTransport delegates SendMessageAsync to HttpListenerServerProvider which will :

public async Task SendEvent(string data, string eventId)
{
    if (_streamWriter == null)
    {
        throw new McpServerException("Stream writer not initialized");
    }
    if (eventId != null)
    {
        await _streamWriter.WriteLineAsync($"id: {eventId}").ConfigureAwait(false);
    }
    await _streamWriter.WriteLineAsync($"data: {data}").ConfigureAwait(false);
    await _streamWriter.WriteLineAsync().ConfigureAwait(false); // Empty line to finish the event
    await _streamWriter.FlushAsync().ConfigureAwait(false);
}

This could be provided by the shared SseResponseStreamTransport. HttpListenerServerProvider could have been folded directly into HttpListenerSseServerTransport (when it was changed from an implementation of an injected provider to a utility class). Using SseResponseStreamTransport would make it possible to do without HttpListenerServerProvider becoming bloated, so it's sounds like a good improvement to me.

[halter73]

Where is this being done?

I added a commit to this PR. 265107f (#47)

[stephentoub]

Where is this being done?

I added a commit to this PR. 265107f (#47)

Ok, cool, so I wasn't going crazy :-) Thanks.