feat(commons): add IAuditWriter and ICentralAuditWriter (#23)

tests/ScadaLink.Commons.Tests/Interfaces/Services/AuditWriterContractTests.cs

@@ -0,0 +1,36 @@
+using System.Reflection;
+using ScadaLink.Commons.Entities.Audit;
+using ScadaLink.Commons.Interfaces.Services;
+
+namespace ScadaLink.Commons.Tests.Interfaces.Services;
+
+/// <summary>
+/// Reflection-level contract guards for the Audit Log (#23) writer interfaces.
+/// Locks in method signature so DI bindings + adapter implementations stay aligned.
+/// </summary>
+public class AuditWriterContractTests
+{
+    [Theory]
+    [InlineData(typeof(IAuditWriter))]
+    [InlineData(typeof(ICentralAuditWriter))]
+    public void WriteAsync_HasExpectedSignature(Type writerType)
+    {
+        var method = writerType.GetMethod("WriteAsync", BindingFlags.Instance | BindingFlags.Public);
+        Assert.NotNull(method);
+        Assert.Equal(typeof(Task), method!.ReturnType);
+
+        var parameters = method.GetParameters();
+        Assert.Equal(2, parameters.Length);
+        Assert.Equal(typeof(AuditEvent), parameters[0].ParameterType);
+        Assert.Equal(typeof(CancellationToken), parameters[1].ParameterType);
+        Assert.True(parameters[1].HasDefaultValue);
+    }
+
+    [Fact]
+    public void IAuditWriter_AndICentralAuditWriter_AreDistinctTypes()
+    {
+        Assert.NotEqual(typeof(IAuditWriter), typeof(ICentralAuditWriter));
+        Assert.False(typeof(IAuditWriter).IsAssignableFrom(typeof(ICentralAuditWriter)));
+        Assert.False(typeof(ICentralAuditWriter).IsAssignableFrom(typeof(IAuditWriter)));
+    }
+}