Add OpenTelemetry support on yarp container

[benjaminpetit]

Add opentelemetry support for the yarp container.

The main issue with the current solution is that when running in Aspire, the container will try to export telemetry to host.docker.internal, which will trigger a SSL error, since the dev cert is only made for localhost .

For the moment, I propose that we ignore this error when running in development.

Other option:

• require the certificate to be present in the docker at runtime, and ignore only the name missmatch
• require the cert to be valid for host.docker.internal, and manually trust the cert at runtime (requiring switching to a non distroless base image)

[MihaZupan]

Nit: If this is otherwise equivalent, can we change this to something like?

builder.Services.Configure<OtlpExporterOptions>(options =>
{
    options.HttpClientFactory = () =>
    {
        var handler = new HttpClientHandler();
    
        if (string.Equals(Environment.GetEnvironmentVariable("YARP_UNSAFE_SKIP_OLTP_CERT_VALIDATION"), "true", StringComparison.InvariantCultureIgnoreCase))
        {
            handler.ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator;
        }
    
        return new HttpClient(handler);
    }
});

builder.Services.AddOpenTelemetry()
    .WithLogging(logging => logging.AddOtlpExporter())
    .WithMetrics(metrics => metrics.AddOtlpExporter())
    .WithTracing(tracing => tracing.AddOtlpExporter());

[MihaZupan]

My comment here was more so about potential subtle differenes in behavior between the two (is the handler configured the same?), not just DangerousAcceptAnyServerCertificateValidator.

Right now it's not obvious that the environment variable will only change the cert validation.

[MihaZupan]

My comment here was more so about potential subtle differenes in behavior between the two (is the handler configured the same?), not just DangerousAcceptAnyServerCertificateValidator.

Right now it's not obvious that the environment variable will only change the cert validation.

[bbartels]

Would really love for this to get merged!