feat: Allow IScopeObserver to observe trace

src/Sentry/IScopeObserver.cs

@@ -29,4 +29,9 @@ public interface IScopeObserver
     /// Sets the user information.
     /// </summary>
     void SetUser(SentryUser? user);
+
+    /// <summary>
+    /// Sets the current trace
+    /// </summary>
+    void SetTrace(SentryId traceId, SpanId parentSpanId);
 }

src/Sentry/Internal/Hub.cs

@@ -255,7 +255,7 @@ public TransactionContext ContinueTrace(
         string? operation = null)
     {
         var propagationContext = SentryPropagationContext.CreateFromHeaders(_options.DiagnosticLogger, traceHeader, baggageHeader);
-        ConfigureScope(scope => scope.PropagationContext = propagationContext);
+        ConfigureScope(scope => scope.SetPropagationContext(propagationContext));
 
         return new TransactionContext(
             name: name ?? string.Empty,

src/Sentry/Internal/ScopeObserver.cs

@@ -81,6 +81,11 @@ public void SetUser(SentryUser? user)
         }
     }
 
+    public void SetTrace(SentryId traceId, SpanId parentSpanId)
+    {
+        throw new NotImplementedException();
+    }
+
     public abstract void SetUserImpl(SentryUser user);
 
     public abstract void UnsetUserImpl();

src/Sentry/Scope.cs

@@ -233,7 +233,7 @@ public ITransactionTracer? Transaction
         }
     }
 
-    internal SentryPropagationContext PropagationContext { get; set; }
+    internal SentryPropagationContext PropagationContext { get; private set; }
 
     internal SessionUpdate? SessionUpdate { get; set; }
 
@@ -376,6 +376,15 @@ public void UnsetTag(string key)
     /// </summary>
     public void AddAttachment(SentryAttachment attachment) => _attachments.Add(attachment);
 
+    internal void SetPropagationContext(SentryPropagationContext propagationContext)
+    {
+        PropagationContext = propagationContext;
+        if (Options.EnableScopeSync)
+        {
+            Options.ScopeObserver?.SetTrace(propagationContext.TraceId, propagationContext.SpanId);
+        }
+    }
+
     /// <summary>
     /// Resets all the properties and collections within the scope to their default values.
     /// </summary>