Add unit tests for CookieNames class functionality

Added a new `CookieNamesTests` class to validate methods in the
`CookieNames` class, including scenarios for generating and
extracting cookie names and keys. Tests cover valid, invalid,
and unrelated cookie names, as well as round-trip validation
of `GetEnvelopeReceiverCookieName` and `GetEnvelopeReceiverKeyOrDefault`.

Updated `DigitalData.Auth.Tests.csproj` to include a project
reference to `DigitalData.Auth.Claims` for testing purposes.

DigitalData.Auth.Tests/Claims/CookieNamesTests.cs

@@ -0,0 +1,120 @@
+using DigitalData.Auth.Claims;
+
+namespace DigitalData.Auth.Tests.Claims;
+
+[TestFixture]
+public class CookieNamesTests
+{
+    private const string DefaultCookieName = "AuthToken";
+    private const string Key = "NTE3YmI5YzUtNjA4Mi00ZTYxLWFhYTUtOTg0NjM4";
+
+    [Test]
+    public void GetEnvelopeReceiverCookieName_ShouldReturnCorrectFormat()
+    {
+        // Arrange
+        var expected = $"{DefaultCookieName}SignFLOWReceiver.{Key}";
+
+        // Act
+        var result = CookieNames.GetEnvelopeReceiverCookieName(DefaultCookieName, Key);
+
+        // Assert
+        Assert.That(result, Is.EqualTo(expected));
+    }
+
+    [Test]
+    public void GetEnvelopeReceiverKeyOrDefault_ShouldReturnKey_WhenCookieNameIsValid()
+    {
+        // Arrange
+        var cookieName = CookieNames.GetEnvelopeReceiverCookieName(DefaultCookieName, Key);
+
+        // Act
+        var result = CookieNames.GetEnvelopeReceiverKeyOrDefault(cookieName, DefaultCookieName);
+
+        // Assert
+        Assert.That(result, Is.EqualTo(Key));
+    }
+
+    [Test]
+    public void GetEnvelopeReceiverKeyOrDefault_ShouldReturnNull_WhenCookieNameHasWrongBase()
+    {
+        // Arrange
+        var cookieName = CookieNames.GetEnvelopeReceiverCookieName("OtherCookie", Key);
+
+        // Act
+        var result = CookieNames.GetEnvelopeReceiverKeyOrDefault(cookieName, DefaultCookieName);
+
+        // Assert
+        Assert.That(result, Is.Null);
+    }
+
+    [Test]
+    public void GetEnvelopeReceiverKeyOrDefault_ShouldReturnNull_WhenCookieNameIsUnrelated()
+    {
+        // Act
+        var result = CookieNames.GetEnvelopeReceiverKeyOrDefault("SomeOtherCookie", DefaultCookieName);
+
+        // Assert
+        Assert.That(result, Is.Null);
+    }
+
+    [Test]
+    public void TryGetEnvelopeReceiverKey_ShouldReturnTrueAndKey_WhenCookieNameIsValid()
+    {
+        // Arrange
+        var cookieName = CookieNames.GetEnvelopeReceiverCookieName(DefaultCookieName, Key);
+
+        // Act
+        var success = CookieNames.TryGetEnvelopeReceiverKey(cookieName, DefaultCookieName, out var key);
+
+        // Assert
+        Assert.Multiple(() =>
+        {
+            Assert.That(success, Is.True);
+            Assert.That(key, Is.EqualTo(Key));
+        });
+    }
+
+    [Test]
+    public void TryGetEnvelopeReceiverKey_ShouldReturnFalse_WhenCookieNameHasWrongBase()
+    {
+        // Arrange
+        var cookieName = CookieNames.GetEnvelopeReceiverCookieName("OtherCookie", Key);
+
+        // Act
+        var success = CookieNames.TryGetEnvelopeReceiverKey(cookieName, DefaultCookieName, out var key);
+
+        // Assert
+        Assert.Multiple(() =>
+        {
+            Assert.That(success, Is.False);
+            Assert.That(key, Is.Null);
+        });
+    }
+
+    [Test]
+    public void TryGetEnvelopeReceiverKey_ShouldReturnFalse_WhenCookieNameIsUnrelated()
+    {
+        // Act
+        var success = CookieNames.TryGetEnvelopeReceiverKey("SomeOtherCookie", DefaultCookieName, out var key);
+
+        // Assert
+        Assert.Multiple(() =>
+        {
+            Assert.That(success, Is.False);
+            Assert.That(key, Is.Null);
+        });
+    }
+
+    [Test]
+    public void GetAndGetOrDefault_ShouldBeInverse_RoundTrip()
+    {
+        // Arrange
+        var cookieName = CookieNames.GetEnvelopeReceiverCookieName(DefaultCookieName, Key);
+
+        // Act
+        var extractedKey = CookieNames.GetEnvelopeReceiverKeyOrDefault(cookieName, DefaultCookieName);
+
+        // Assert
+        Assert.That(extractedKey, Is.EqualTo(Key));
+    }
+}