Provide MapOpenTelemetryPrometheusScrapingEndpoint() extension method for IEndpointRouteBuilder

[msschl]

Feature Request

Is your feature request related to a problem?

In internal clusters, the /metrics endpoint sometimes should not be exposed to the public. Therefore, in ASP.Net Core you can map an endpoint to a specific port and expose that port only to cluster internal traffic.

Describe the solution you'd like:

Provide an MapOpenTelemetryPrometheusScrapingEndpoint extension returning an IEndpointConventionBuilder to allow further configuration of the enpoint like required hosts.

namespace Microsoft.AspNetCore.Builder
{
    public static class PrometheusExporterEndpointRouteBuilderExtensions
    {
        public static IEndpointConventionBuilder MapOpenTelemetryPrometheusScrapingEndpoint(this IEndpointRouteBuilder endpoints, string pattern, MeterProvider meterProvider = null);
    }
}

[msschl]

Fixed by #3295