feat(telemetry): MapZbMetrics Prometheus scrape endpoint

ZB.MOM.WW.Telemetry/src/ZB.MOM.WW.Telemetry/ZbMetricsEndpointExtensions.cs

@@ -0,0 +1,22 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Routing;
+
+namespace ZB.MOM.WW.Telemetry;
+
+/// <summary>
+/// Endpoint extension for mounting the Prometheus <c>/metrics</c> scrape endpoint.
+/// </summary>
+public static class ZbMetricsEndpointExtensions
+{
+    /// <summary>
+    /// Mounts the Prometheus <c>/metrics</c> endpoint. Only valid when
+    /// <see cref="ZbTelemetryOptions.Exporter"/> = <see cref="ZbExporter.Prometheus"/>.
+    /// Call after <c>app.UseRouting()</c>.
+    /// </summary>
+    /// <param name="endpoints">The endpoint route builder.</param>
+    public static IEndpointConventionBuilder MapZbMetrics(this IEndpointRouteBuilder endpoints)
+    {
+        ArgumentNullException.ThrowIfNull(endpoints);
+        return endpoints.MapPrometheusScrapingEndpoint();
+    }
+}

ZB.MOM.WW.Telemetry/tests/ZB.MOM.WW.Telemetry.Tests/MapZbMetricsTests.cs

@@ -0,0 +1,38 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.Extensions.Hosting;
+using ZB.MOM.WW.Telemetry;
+
+namespace ZB.MOM.WW.Telemetry.Tests;
+
+public sealed class MapZbMetricsTests
+{
+    [Fact]
+    public async Task MapZbMetrics_ServesPrometheusEndpoint()
+    {
+        var builder = WebApplication.CreateBuilder();
+        builder.WebHost.UseUrls("http://127.0.0.1:0");
+        builder.AddZbTelemetry(o =>
+        {
+            o.ServiceName = "t";
+            o.Exporter = ZbExporter.Prometheus;
+            o.Meters = ["Test.Meter"];
+        });
+
+        await using var app = builder.Build();
+        app.MapZbMetrics();
+
+        await app.StartAsync();
+
+        var address = app.Urls.First();
+        using var client = new HttpClient { BaseAddress = new Uri(address) };
+
+        var response = await client.GetAsync("/metrics");
+
+        Assert.Equal(System.Net.HttpStatusCode.OK, response.StatusCode);
+        Assert.NotNull(response.Content.Headers.ContentType);
+        Assert.Equal("text/plain", response.Content.Headers.ContentType!.MediaType);
+
+        await app.StopAsync();
+    }
+}