1.7 ApiKey value type

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/FrameProcessor.Tests/ApiKeyTests.cs

@@ -0,0 +1,78 @@
+using FrameProcessor.Domain;
+
+namespace FrameProcessor.Tests;
+
+public class ApiKeyTests
+{
+    [Fact]
+    public void Matches_ReturnsTrue_ForIdenticalKey()
+    {
+        var key = new ApiKey("s3cret-value");
+        Assert.True(key.Matches("s3cret-value"));
+    }
+
+    [Fact]
+    public void Matches_ReturnsFalse_ForDifferentKey()
+    {
+        var key = new ApiKey("s3cret-value");
+        Assert.False(key.Matches("wrong"));
+    }
+
+    [Fact]
+    public void Matches_ReturnsFalse_ForKeyOfDifferentLength()
+    {
+        var key = new ApiKey("s3cret");
+        Assert.False(key.Matches("s3cret-value"));
+        Assert.False(key.Matches("s3cre"));
+    }
+
+    [Fact]
+    public void Matches_ReturnsFalse_ForNull()
+    {
+        var key = new ApiKey("s3cret");
+        Assert.False(key.Matches(null));
+    }
+
+    [Fact]
+    public void Matches_ReturnsFalse_ForEmptyCandidate_WhenKeyIsNotEmpty()
+    {
+        var key = new ApiKey("s3cret");
+        Assert.False(key.Matches(string.Empty));
+    }
+
+    [Fact]
+    public void Matches_IsCaseSensitive()
+    {
+        var key = new ApiKey("Secret");
+        Assert.False(key.Matches("secret"));
+        Assert.False(key.Matches("SECRET"));
+    }
+
+    [Fact]
+    public void Matches_HandlesMultiByteUtf8()
+    {
+        var key = new ApiKey("nyckel-äöå");
+        Assert.True(key.Matches("nyckel-äöå"));
+        Assert.False(key.Matches("nyckel-aoa"));
+    }
+
+    [Fact]
+    public void Constructor_ThrowsOnNull()
+    {
+        Assert.Throws<ArgumentNullException>(() => new ApiKey(null!));
+    }
+
+    [Fact]
+    public void Value_ReturnsConfiguredString()
+    {
+        var key = new ApiKey("abc");
+        Assert.Equal("abc", key.Value);
+    }
+
+    [Fact]
+    public void DefaultStruct_Value_IsEmpty()
+    {
+        var key = default(ApiKey);
+        Assert.Equal(string.Empty, key.Value);
+    }
+}