Make sure a traceparent is always present even if we are not authenti…

…cated.

Don't assume there is alwasys a non-null activity.
Use the header dictionary for searching header values.

src/Arc4u.Standard.OAuth2.AspNetCore/Middleware/AddContextToPrincipalMiddleware.cs

@@ -8,7 +8,6 @@
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Primitives;
 
 namespace Arc4u.OAuth2.Middleware;
 public class AddContextToPrincipalMiddleware
@@ -29,26 +28,32 @@ public async Task Invoke(HttpContext context)
     {
         ArgumentNullException.ThrowIfNull(context);
 
-        if (context.User is not null && context.User is AppPrincipal principal && principal.Identity is not null && principal.Identity.IsAuthenticated)
-        {
-            using var activity = _activitySource?.StartActivity("Add context to Arc4u Principal", ActivityKind.Producer);
+        // Note that the action of setting a traceparent and adding context to the principal are conceptually separate, but they are viewed as one "activity" for the purposes of logging.
 
-            // Ensure we have a traceparent.
+        using var activity = _activitySource?.StartActivity("Add context to Arc4u Principal", ActivityKind.Producer);
+
+        // We may have a null current activity if we are not in the context of an activity.
+        // we may not be in the context of an activity if either (1) there is no _activitySource or (2) the activity has no active listeners
+        if (Activity.Current is not null)
+        {
+            // Ensure we have a traceparent, whether we are authenticated or not, since it's always useful to have a traceparent.
             if (!context.Request.Headers.ContainsKey("traceparent"))
             {
-                // Activity.Current is not null just because we are in the context of an activity.
-                context.Request.Headers.Add("traceparent", Activity.Current!.Id);
+                // Activity.Current is not null because we are in the context of an activity.
+                context.Request.Headers.Add("traceparent", Activity.Current.Id);
             }
 
-            activity?.SetTag(LoggingConstants.ActivityId, Activity.Current!.Id);
+            activity?.SetTag(LoggingConstants.ActivityId, Activity.Current.Id);
+        }
 
-            // Check for a culture.
-            var cultureHeader = context.Request?.Headers?.FirstOrDefault(h => h.Key.Equals("culture", StringComparison.InvariantCultureIgnoreCase));
-            if (cultureHeader.HasValue && StringValues.Empty != cultureHeader.Value.Value && cultureHeader.Value.Value.Any())
+        if (context.User is not null && context.User is AppPrincipal principal && principal.Identity is not null && principal.Identity.IsAuthenticated)
+        {
+            // Check for a culture. The header dictionary takes care of the proper matching of the header name.
+            if ((context.Request?.Headers?.TryGetValue("culture", out var cultureHeader) ?? false) && cultureHeader.Any())
             {
                 try
                 {
-                    principal.Profile.CurrentCulture = new CultureInfo(cultureHeader.Value.Value[0]);
+                    principal.Profile.CurrentCulture = new CultureInfo(cultureHeader[0]);
                 }
                 catch (Exception ex)
                 {