Add NoAuthenticationStrategy and unit tests

Introduced the `NoAuthenticationStrategy` class in the `FlowSynx.Client.Authentication` namespace, implementing the `IAuthenticationStrategy` interface. This class applies no authentication to HTTP requests, with the `ApplyAsync` method being a no-op.

Added unit tests in `NoAuthenticationStrategyTests` to verify:
- `ApplyAsync` does not set an `Authorization` header on requests without one.
- `ApplyAsync` does not modify an existing `Authorization` header.

#63

Author: ziagham

src/FlowSynx.Client/Authentication/NoAuthenticationStrategy.cs

@@ -0,0 +1,16 @@
+namespace FlowSynx.Client.Authentication;
+
+/// <summary>
+/// Represents an authentication strategy that applies no authentication to HTTP requests.
+/// Implements the <see cref="IAuthenticationStrategy"/> interface.
+/// </summary>
+public class NoAuthenticationStrategy : IAuthenticationStrategy
+{
+    /// <summary>
+    /// Applies no authentication to the given HTTP request.
+    /// This method is a no-op and does not modify the request.
+    /// </summary>
+    /// <param name="request">The HTTP request to which no authentication will be applied.</param>
+    /// <returns>A task representing the asynchronous operation.</returns>
+    public Task ApplyAsync(HttpRequestMessage request) => Task.CompletedTask;
+}

tests/FlowSynx.Client.UnitTests/Authentication/NoAuthenticationStrategyTests.cs

@@ -0,0 +1,37 @@
+using FlowSynx.Client.Authentication;
+
+namespace FlowSynx.Client.UnitTests.Authentication;
+
+public class NoAuthenticationStrategyTests
+{
+    [Fact]
+    public async Task ApplyAsync_DoesNotSetAuthorizationHeader()
+    {
+        // Arrange
+        var strategy = new NoAuthenticationStrategy();
+        var request = new HttpRequestMessage();
+
+        // Act
+        await strategy.ApplyAsync(request);
+
+        // Assert
+        Assert.Null(request.Headers.Authorization);
+    }
+
+    [Fact]
+    public async Task ApplyAsync_DoesNotModifyExistingAuthorizationHeader()
+    {
+        // Arrange
+        var strategy = new NoAuthenticationStrategy();
+        var request = new HttpRequestMessage();
+        request.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", "existing-token");
+
+        // Act
+        await strategy.ApplyAsync(request);
+
+        // Assert
+        Assert.NotNull(request.Headers.Authorization);
+        Assert.Equal("Bearer", request.Headers.Authorization.Scheme);
+        Assert.Equal("existing-token", request.Headers.Authorization.Parameter);
+    }
+}