Added MetricsUrl for HttpMetricsMiddleware

Prometheus.AspNetCore/HttpMetrics/HttpMiddlewareExporterOptions.cs

@@ -10,11 +10,16 @@ public sealed class HttpMiddlewareExporterOptions
         public HttpRequestDurationOptions RequestDuration { get; set; } = new HttpRequestDurationOptions();
 
         /// <summary>
-        /// Whether to capture metrics for queries to the /metrics endpoint (where metrics are exported by default). Defaults to false.
-        /// This matches against URLs starting with the /metrics string specifically - if you use a custom metrics endpoint, this will not match.
+        /// Whether to capture metrics for queries to the MetricsUrl endpoint. Defaults to false.
         /// </summary>
         public bool CaptureMetricsUrl { get; set; }
 
+        /// <summary>
+        /// The Url used for the CaptureMetricsUrl property.
+        /// This defaults to /metrics where metrics are exported by default
+        /// </summary>
+        public string MetricsUrl { get; set; } = "/metrics";
+
         /// <summary>
         /// Configures all the different types of metrics to use reduced status code cardinality (using 2xx instead of 200, 201 etc).
         /// </summary>

Prometheus.AspNetCore/HttpMetricsMiddlewareExtensions.cs

@@ -62,7 +62,7 @@ void ApplyConfiguration(IApplicationBuilder builder)
             if (options.CaptureMetricsUrl)
                 ApplyConfiguration(app);
             else
-                app.UseWhen(context => context.Request.Path != "/metrics", ApplyConfiguration);
+                app.UseWhen(context => context.Request.Path != options.MetricsUrl, ApplyConfiguration);
 
             return app;
         }