Set resource name after exception in OnEndRequest method (#8439)

When no resource-based sampling rules are configured, the resource name
was only set in OnEndRequest. If OnEndRequest doesn't complete (e.g.,
client disconnect), the resource name remained null and defaulted to the
operation name aspnet.request in Span.Finish(). This fix ensures the
resource name is always set early in OnBeginRequest. Fixes APMS-19184

Made-with: Cursor

## Summary of changes

## Reason for change
https://datadoghq.atlassian.net/browse/APMS-19184

## Implementation details

## Test coverage

## Other details


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---------

Co-authored-by: NachoEchevarria <ignacio.echevarria@datadoghq.com>
Co-authored-by: NachoEchevarria <53266532+NachoEchevarria@users.noreply.github.com>
Co-authored-by: Andrew Lock <andrew.lock@datadoghq.com>

Author: 3 people

tracer/src/Datadog.Trace/AspNet/TracingHttpModule.cs

@@ -1,4 +1,4 @@
-// <copyright file="TracingHttpModule.cs" company="Datadog">
+// <copyright file="TracingHttpModule.cs" company="Datadog">
 // Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2 License.
 // This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2017 Datadog, Inc.
 // </copyright>
@@ -130,10 +130,10 @@ private void OnBeginRequest(object sender, EventArgs eventArgs)
             Scope scope = null;
             Scope inferredProxyScope = null;
             bool shouldDisposeScope = true;
+            var tracer = Tracer.Instance;
+
             try
             {
-                var tracer = Tracer.Instance;
-
                 if (!tracer.CurrentTraceSettings.Settings.IsIntegrationEnabled(IntegrationId))
                 {
                     // integration disabled
@@ -263,6 +263,18 @@ private void OnBeginRequest(object sender, EventArgs eventArgs)
                 if (shouldDisposeScope)
                 {
                     // Dispose here, as the scope won't be in context items and won't get disposed on request end in that case...
+                    try
+                    {
+                        if (scope?.Span is { ResourceName: null } span)
+                        {
+                            span.ResourceName = BuildResourceName(tracer, (sender as HttpApplication)?.Context?.Request);
+                        }
+                    }
+                    catch (Exception ex2)
+                    {
+                        Log.Debug(ex2, "Unable to set fallback resource name.");
+                    }
+
                     scope?.Dispose();
                     inferredProxyScope?.Dispose();
                 }
@@ -417,6 +429,18 @@ private void OnEndRequest(object sender, EventArgs eventArgs)
                     }
                     finally
                     {
+                        try
+                        {
+                            if (scope.Span.ResourceName is null)
+                            {
+                                scope.Span.ResourceName = BuildResourceName(tracer, app.Request);
+                            }
+                        }
+                        catch (Exception ex)
+                        {
+                            Log.Debug(ex, "Unable to set fallback resource name.");
+                        }
+
                         scope.Dispose();
                         proxyScope?.Dispose();
                         // Clear the context to make sure another TracingHttpModule doesn't try to close the same scope