Adding an AsyncLocalTransactionContextPropagator.

Signed-off-by: André Silva <2493377+askpt@users.noreply.github.com>

src/OpenFeature/AsyncLocalTransactionContextPropagator.cs

@@ -0,0 +1,25 @@
+using System.Threading;
+using OpenFeature.Model;
+
+namespace OpenFeature;
+
+/// <summary>
+///  It is a no-op implementation of <see cref="ITransactionContextPropagator"/>
+///  It uses the <see cref="AsyncLocal{T}"/> to store the transaction context.
+/// </summary>
+public sealed class AsyncLocalTransactionContextPropagator : ITransactionContextPropagator
+{
+    private readonly AsyncLocal<EvaluationContext> _transactionContext = new();
+
+    /// <inheritdoc />
+    public EvaluationContext GetTransactionContext()
+    {
+        return this._transactionContext.Value ?? EvaluationContext.Empty;
+    }
+
+    /// <inheritdoc />
+    public void SetTransactionContext(EvaluationContext evaluationContext)
+    {
+        this._transactionContext.Value = evaluationContext;
+    }
+}