Enable ALPN tests/features on MAC

[Tratcher]

Is there an existing issue for this?

• I have searched the existing issues

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

• Server side ALPN support for SslStream on Mac runtime#27727
  This feature is now available from the runtime so we should consume it in Kestrel.

Describe the solution you'd like

Areas of interest:

• Kestrel HTTP/2 tests
• Kestrel Mac specific error messages
• gRPC tests
• gRPC template
• Kestrel docs
• gRPC docs

Additional context

No response

[JamesNK]

gRPC template?

Yes. There is at least a comment about macOS to remove.

There are also a lot of docs that need to be updated. Let's focus on making sure this technically works first before thinking about them.

[halter73]

We probably want to remove this check which preemptively stops you from binding to HTTP/2-only TLS endpoint on macOS at application startup. We already have logic in Kestrel's HttpConnection to fail at connection start if h2 isn't negotiate via ALPN on a HTTP/2-only TLS endpoint.

aspnetcore/src/Servers/Kestrel/Core/src/Middleware/HttpsConnectionMiddleware.cs

Lines 466 to 472 in 53124ab

	// This configuration will always fail per-request, preemptively fail it here. See HttpConnection.SelectProtocol().
	if (httpProtocols == HttpProtocols.Http2)
	{
	if (OperatingSystem.IsMacOS())
	{
	throw new NotSupportedException(CoreStrings.Http2NoTlsOsx);
	}

@JamesNK suggests it might make sense to ask for something along the lines of a static IsAlpnSupported property on SslStream to support this use case.

[JamesNK]

Consider waiting for dotnet/runtime#79687 before looking at this.

Edit: This API will probably take some time to make it through triage/review/implementation. Rather than block this, I think we could have a pretend internal API, and check that in places we currently check for macOS.

[adityamandaleeka]

@JamesNK Is this issue at this point just to track using the new proposed runtime API? Should it be remilestoned?

[JamesNK]

Updating docs for .NET 8 can happen in preview 1.