chore: import upstream snapshot with attribution

dotnet/samples/GettingStartedWithProcesses/Step04/ChatHistoryProvider.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft. All rights reserved.
+using Microsoft.SemanticKernel.ChatCompletion;
+
+namespace Step04;
+
+/// <summary>
+/// Provider based access to the chat history.
+/// </summary>
+/// <remarks>
+/// While the in-memory implementation is trivial, this abstraction demonstrates how one might
+/// allow for the ability to access chat history from a remote store for a distributed service.
+/// <code>
+/// class CosmosDbChatHistoryProvider(CosmosClient client, string sessionId) : IChatHistoryProvider { }
+/// </code>
+/// </remarks>
+internal interface IChatHistoryProvider
+{
+    /// <summary>
+    /// Provides access to the chat history.
+    /// </summary>
+    Task<ChatHistory> GetHistoryAsync();
+
+    /// <summary>
+    /// Commits any updates to the chat history.
+    /// </summary>
+    Task CommitAsync();
+}
+
+/// <summary>
+/// In memory based specialization of <see cref="IChatHistoryProvider"/>.
+/// </summary>
+internal sealed class ChatHistoryProvider(ChatHistory history) : IChatHistoryProvider
+{
+    /// <inheritdoc/>
+    public Task<ChatHistory> GetHistoryAsync() => Task.FromResult(history);
+
+    /// <inheritdoc/>
+    public Task CommitAsync()
+    {
+        return Task.CompletedTask;
+    }
+}